Is it possible to setup a FreeBSD/Linux computer to compile binaries or DLL's for a mac running OSX? I wanted to compile updates for a mac but not really develop on a mac, kind of a weird request but its because PC's are cheaper and more powerful when it comes to stuff like this. I have an old power book G3 running OSX, but I'd rather do compiling on my spare Athlon64 3ghz computer.

The easiest solution would be to download an ISO of Apple's Darwin operating system. I believe it comes with a gcc/binutils package that can target i386 and PowerPC (and build fat binaries!). If not you'd just have to fetch Apple's gcc sources and build your own cross-compiler.

http://developer.apple.com/darwin/projects/darwin/