I'm trying to find a least-resistance path from C# to C++, and while I feel I handle C# pretty well after two solid years, I'm still not sure I've gotten the "groove" of C++, despite numerous attempts.
Are there any particular books or websites that might be suitable for this transition?
I suggest you to read The C++ Programming Language book (written by Bjarne Stroustrup). It may not be the best book to begin with, but it is definitely on you should read, sooner or later.
I recommend The C++ Programming language by Bjarne Stroustrup. It's not a suitable book for new programmers, but I found it quite effective as programmer who was experiences in other languages and didn't want to waste too much time with learning how while loops work. It's a dense but quite comprehensive book.
I'd consider K&R a prerequisite for C++. Perhaps the best thing about C++ is that it's a better C.
And of course, Stroustrup (as suggested by Mladen Jankovic) is a must read.
My two standard books are "Object-Oriented Programming in C++", Third Edition, by Robert LaFore, published by The Waite Group, and "C++ from the Ground Up" by Herbert Shildt, published by Osborne McGraw-Hill.
They are fundamentally very different beasts so there is no least resistance path between. However I recommend you to read http://www.phpcompiler.org/doc/virtualinheritance.html beforehand in case you ever need a non-trivial inheritance. It can save you a few headaches.
The C++ Programming Language by Bjarne Stroustrup is a must read. Effective C++ (Scott Meyers) is another book I found helpful.
And to balance all this, read the C++ FQA ( http://yosefk.com/c++fqa/ ) - while not a book, it's a valuable resource, and I wish I had access to it when I was getting started with C++. Just don't let it discourage you.
I found Lippman et al's "C++ Primer: 4th edition" to be excellent. It emphasizes STL usage, best practices, and auto_ptr usage from the very first. I went from a Java position to a C++ assignment, and it was really excellent.
As a pure reference, Josuttis's "The C++ Standard Library" was STL at its best (and worst...the guy really doesn't pull punches)
Lastly, Meyer's Effective C++, as others have said is a must-read for the "gotchas" inherent in C++
About two years ago, I made the switch from C# to C++ (after 10 years of writing java). The most useful book for me was Bruce Eckel's Thinking in C++ [AMZN]. You can also read the book online at Eckel's website. It's a well-written book--the kind you can read in bed--that's also useful as a keyboard-side reference. It assumes a significant level of comfort with OO and general programming concepts.
Stroustrup [AMZN] is invaluable as a reference, but basically impenetrable unless you're trying to answer a very specific question--and even then, it's a struggle. I haven't cracked my K&R [AMZN] in a few years. I don't think it's got much value as a C++ reference. Myers' Effective C++ [AMZN] (and, once you get there, Effective STL [AMZN]) are fantastic books. They're very specific, though (e.g., "36. Design functor classes for pass-by-value"), and hence not as useful as Eckel for making the transition.
My experience writing C++ after many years writing managed languages has been great. C++ is a hundred times more expressive than C#, and extremely satisfying to write--where it's warranted. On the other hand, on the rare occasions when I still get to write C#, I'm always amazed by how quickly and succinctly I can get things done.
Anyway, Eckel's Effective C++ can help you make the transition. There's a second volume that's good, but not as good. Stick with the original.
Good luck!
4: http://www.amazon.com/Programming-Language-Prentice-Hall-Software/dp/0131103628/ref=pd_bbs_1?ie=UTF8&s=books&qid=1221539310&sr=1-1 AMZN
This is a list of books that are recommended by the folks over in #C++ EFNet: http://rafb.net/efnet_cpp/books/