There is a way yes, I can't remember the name of the program at the moment. I'm sure someone else can provide that.
However I have read it is stupidly slow. Alot slower than emulating windows on a mac. PC CPU's just don't cut it for emulation. So while a Dual 2.5Ghz G5 might emulate a usable 1Ghz Pentium PC, a Dual Pentium 3ghz system running the OS X emulator will feel like a 50Mhz mac.
It's pretty much useless except for the novelty value or if there is something small you really really desperately need to do in OS X.