I would like to write some Objective-C code for distribution. What is the best way to package up the output. In Java you can package up your code in a JAR file and distribute that. What would be the equivalent in Objective-C?
The following link is close, but seems to address more of the namespace issues which I am not concerned about. I am mostly concerned about setting the code up for easy distribution.
http://stackoverflow.com/questions/1000707/objective-c-equivalent-of-java-packages
You want to create a Framework. There is a starting point in Xcode for a new project to create one of these. There are a few caveats and gotchas, but on the whole the process is straightforward.
Edit: For clarification: If you are planning to distribute it as FOSS; packing it up in a framework might be overkill; just distributing the source code might be a more sensible and simpler option. But if you would like to keep the source to yourself or distribute it with a collection of relevant resources, a framework might definitely be a good idea.
Reedit: For an introduction, see http://developer.apple.com/documentation/MacOSX/Conceptual/BPFrameworks/
You didn't say if it was for iPhone or not. On the iPhone, it needs to be a .sa (statically linked library) -- but I think the normal distribution would by a .dylib or .so
Java programs run in the context of a virtual machine. Jar contains abstract bytecodes which must be converted into native machine code by the VM.
Objective-C, like C, is compiled into native machine code, such as a Win .exe file, directly runnable by the operating system.
Most programs of any complexity consist of more than a single file and include DLLs, icon files, etc. The configuration of your files for distribution would usually be handled by a setup utility.
A framework is almost certainly the way to go. One of the really nice things about Frameworks on OS X is that they can bundle the executable code, headers, metadata, images, icons, etc. in a single package. Further, frameworks can be included in */Library/Frameworks/ or even inside your app bundle to completely decouple from any other app's dependency on a given version of the framework.
Apple's Framework Programming Guide is the best place to get started with frameworks.
Creating a framework is simple. Basically, in Xcode you choose File > New Project... and select Framework, then Cocoa Framework. This will set up a new project with framework target and automatically package everything up for you when you build.
Don't forget that documentation and unit tests are a Good Thing™, especially for frameworks, which are inherently more likely to be used by multiple clients than most end-user code. You can add more targets to your framework Xcode project to document and test it.
Since you're looking for examples, check out CHDataStructures.framework (a project which I develop) and PSMTabBarControl.framework (which includes lots of extra resources in the framework). Both are open-source, and should provide adequate examples for rolling your own.
One word of advice to save you some head-scratching: your header files will not be copied to the built framework unless you click on the framework target and change the Role to "Public" (or "Private").
You could compile it as a Framework or as a static library (.so I believe).