I've been learning C: it's a beautiful, well-thought-out language. However, it is so low-level that writing any sort of major project becomes tedious.
What higher-level language has the most C-like syntax—but without all the clutter that you find in something like C++. Does one exist?
Probably Java and C#... Java a little more so I think.
And it's not the language - it's all about the libraries. Try out Qt (http://qt.nokia.com/). It's for C++ and I know you said C but I'm just making a point that you'll find yourself writing just as little (and perhaps even less!) code than you'd write for applications in Java or C#. Plus they're native and cross-platform.
All about the libraries.
This is too broad a question and is best made Community wiki.
However, in my mind, the main distinguishing feature of C is it's compactness. The whole language can be described in a small book like K&R. One can remember all the syntactic details without much effort (since there are so few of them) and it doesn't try to protect it's users from themselves.
Languages like C++ are much more baroque. It's quite hard to remember all the rules and exceptions. I feel the same way about Perl and Ruby. There are lots of things to remember and lots of things to watch out for.
I feel the same sense of compactness with Python (although perhaps not as much as C). There's very little "special syntax" and all libraries and modules are operated upon in a similar fashion.
This (probably like most other comments on this question) is a personal evaluation and is by no means a final word.
Google's Go language has a similar syntax (though different enough I suppose) and semantics, though with garbage collection, polymorphism, etc., built into the language.
This comparison of basic instructions gives you a good idea of what languages are similar to each other.
I would say PHP is most like C except for the $variables, if you can distinguish php the language from php the platform. Java tries in some ways, but is too strongly object oriented to be similar to C.
I'd vote C#. I don't know what you mean by "clutter," but from a usability standpoint, C# is nice because it avoids some of the tedious things of C++, like having to essentially "declare" each of your class's methods twice (prototyping it in the header file, then essentially duplicating the same thing in your class's implementation). Ditching header files was nice in other ways too, like doing away with dependency conflicts in big projects or avoiding circular references. In C#, the compiler takes care of all that (although you still have to set references to other files or assemblies).
I've been doing C# for 10 years and I still miss pointers, which believe it or not, in my opinion, actually made debugging easier!
If you're going to be programming often, it's good to know languages that are explicitly not like each other. It's especially useful to know high level scripting languages like python or ruby. If you can think like a programmer in C you should be fine learning either of these two. Many big projects take advantage of the rapid prototyping of higher level languages like python or ruby, but also take advantage of low overhead (fast) compiled languages like C/C++.
I've been learning C: it's a beautiful, well-thought-out language. However, it is so low-level that writing any sort of major project becomes tedious.
Some people would say that the second sentence proves that the assertion of the first sentence is false.
Another point is that this is pretty much unanswerable. What is a "high level" language? what are your criteria for "closeness"? Syntax, computational model, performance? And what kind of applications are you wanting to build with this hypothetical language?
And if you just want to confine yourself to languages that "look like" C, why? As someone who has lost count of the number of programming languages he has used, I can tell you that differences in programming language syntax are generally pretty unimportant. You can get used to pretty much any syntax, given time.
The D programming language is an attempt to be what C++ should have been (not bashing on C++ at all it is my primary language) and I quote from the website, "D is a systems programming language. Its focus is on combining the power and high performance of C and C++ with the programmer productivity of modern languages like Ruby and Python. Special attention is given to the needs of quality assurance, documentation, management, portability and reliability. " The issue with D is it is relatively new compared to a lot of languages but luckily it can still use C libraries which allows it to access a large pre-existing code base. Certainly worth checking out.
Java is another option however it is notably slower than C. Syntactically it is very similar and offers a nice object orientated environment for writing code. It is also considered by most to be a safer language than C and C++. It is widely used in enterprise.
Python while syntactically not like C is a high level Object Orientated Programming Language that is very popular and can import C modules which may be very useful down the track.
In C++ you can write C code and have it compile successfully as C++ (mostly). Therefore, although I suggest that your term "clutter" is both derogatory and ambiguous, the only clutter you will have is what you choose to write yourself. You can use C++ as a bigger tool-bag without using all the tools (or clutter if you prefer).
The answer therefore is C++ whether you like it or not. Most other C-like languages add OO features, which is perhaps what you regard as clutter, but you do not get something for nothing and you need to have syntax to support the additional features. Such languages include:
Of these Objective-C is probably the most C-Like since it is a superset of C in the way that C++ is not quite. It is also the preferred language for OSX and iPhone/iPod Touch development, which may be attractive.
Java is ubiquitous but probably best described as superficially C-like. C# has limited cross-platform support but is the path of least resistance for Windows GUI development with excellent free development tools. C# also has a simpler but more restrictive OO implementation than C++ so may meet your requirements, but its resemblance to C/C++ can be misleading; it is fundamentally different in how it works in a similar manner to Java. D is somewhat of a niche, being developed by a single author (albeit the author of the once renowned Zortech/Symantec C++ compiler).
Regarding it being "low level" and "tedious", when embarking on a "major project", you would seldom start from scratch with only the standard library and OS API available, you would make use of third-party and in-house developed libraries to quickly develop higher level functionality. That said, an OO approach is generally much more amenable to this 'code-reuse' approach, and of course C++'s standard library and third-party libraries are more extensive (not least because it can use C libraries as well as C++ libraries). In fact I would suggest that apart form support for OO, the only thing that makes C++ higher-level is its extensibility via classes as first-class objects. It remains suitable as a systems-level language nonetheless.
Javascript has a reasonably C-like syntax, and it's a very popular language. Javascript has a lot of quirks, but it has one powerful similarity to C - it's simple. The complete Javascript specification is very short, and the language is very powerful and high-level. It would be great to clean it up from some of its ugly cruft, though.
I'll just point out that Pascal is semantically (though not so much syntactically) very similar to C, so there are options like Object Pascal, Modula 2, Ada and Oberon out there where you will be re-using most of the non-trivial part of what you already know, the trivial part being the spelling.
You're probably better off sticking with C# or Java in terms of job prospects, though.
EDIT
I'll also add that on the clutter issue, it is important to sort out which clutter is important. C has less "clutter" in it's language definition, true, but the relevant clutter is in source code. Consider the following...
// C
struct mystruct *myvar;
myvar = (struct mystruct *) malloc (sizeof (struct mystruct));
myvar->a = 1;
myvar->b = 2;
myvar->c = 3;
call_something (myvar);
free (myvar);
// C++
auto_ptr<mystruct> myvar (new myclass (1, 2, 3));
call_something (myvar);
The point is that the "clutter" in the language definition is there for a reason. With a little up-front work when writing libraries, a lot of work (and clutter) is avoided down the line. And even when you're writing a library, you benefit from the up-front work done by other library writers.
If you think that C++ is cluttered, then you just don't know how to write effective C++, because nobody forces you to use any of the advanced tools available. You could write a C++ program entirely in C plus your favourite C++ feature (like the AWESOME standard library). That's the definition of uncluttered. A cluttered language would be Java/C#, where you HAVE to put every function in a class. That's clutter.
What higher-level language has the most C-like syntax—but without all the clutter that you find in something like C++?
I'm going to answer a slightly different question:
What is a language that is like C in that it is well designed and beautifully thought out, is like C in that it is good for systems programming, allows people to program at a higher level than C, and is relatively uncluttered?
I don't think this question has a single right answer, but here are three worthy candidates (in alphabetical order):
D. The D language is designed essentially as a better, cleaner C++. Like C++, D is explicitly designed to incorporate a lot of features, but one hopes in a cleaner, more harmonious way than C++. A major difference that enables programmers to work at a higher level is that memory is managed automatically by the language and safety is guaranteed by the compiler (and run-time system) through garbage collection.
Go. Go scores very high on being well designed and beautifully thought out: Rob Pike is a master designer and has been practicing this particular craft for 25 years. Its explicit goal is to be uncluttered and to make systems programming "fun again". Go is still a new language, and Rob has learned much from Squeak, Newsqueak, Alef, and Limbo. Because Rob understands that a great design is one with no unnecessary parts, Go is clean and uncluttered. Its primary features that are higher-level than C are type safety, garbage collection, and an excellent concurrency model.
Java. Java has a well-designed core (see Jim Waldo's book Java: The Good Parts) but unfortunately suffers from the clutter that any mature, successful language accumulates. The features of Java that make it most suitable for higher-level programming are interfaces, garbage collection, and exceptions.
The common thread here is using garbage collection to relieve the programmer of the burden of memory management. This is a major boost to productivity.
Each of these languages has much to recommend it. My own taste is for languages that are small and simple, and I admire Rob Pike's body of work very highly, so if I had to pick one for myself, it would be Go, despite the fact that it is new and unproven.