As I mentioned in my introduction, I use .NET for all of my development, even on OS X. It should be easy to translate my examples from C# to another language — they are very simple, and mostly calls to system functions — but in case you are interested in trying .NET out for yourself, here is a short introduction.
First, you’ll need to install Mono, an open source implementation of .NET managed by Novell. It is delivered as a .dmg which you install like any other application. Mono includes all of the necessary libraries as well as compilers for C#, VB.NET, IronPython, with more in the works. I happen to like C#, but there are lots of other language options out there.
Whatever language you choose, you’ll eventually want to compile it. For the simple examples in this guide a few commands entered at the terminal are all that is needed. Larger projects, at the time of this writing, are a bit more troublesome. There is a C# plugin for XCode under development (which I really should try one of these days). If you have the budget, there is a nice looking cross-platform IDE available from Omnicore. And of course you can use makefiles (I’m working on a tool called Premake that can generate those for you if you want).
I actually cheat: I run Visual Studio 2005 in Parallels, build to a folder shared with OS X, then hop over to a terminal window to run it. If this sounds like something you want to try, you can get the Express versions of Visual Studio for free.
If someone has a better way I’d love to hear about it (and if anyone from Omnicore wants to send me copy of XDevelop, I’m okay with that too).