yes it can be done, depending on you hardware choice's it makes it harder or very easy to do.
I am just getting into the world of mac, before now I wouldn't touch them. I picked up a g3 clamshell at goodwill for 2 dollars that came with the yo-yo and a dead battery. Other then that it ran fine. I upgraded the hard drive to a 30 gb and installed OS X .3.9 (It had OS 8.6) on it and upgraded the ram to 544mb and put a airport card in it and put a new battery in it. I have around $80 bucks into it, and it is letting me check out macs OS.
I find ICP's version is nice to work with on Hackins, but do check out osx86projects site if your really interested in trying to build you own. Good luck