Not as such, though you have a few really good options:
- You can run LinuxPPC separately to Mac OS X, allowing you to boot into one or the other as desired.
- You can usually install software from Gnu/Linux in Mac OS X, using programs such as Fink to port the software into your system.
- You can run a PC linux version on VirtualPC.
What is it you want to run or do? We can help point you in the right direction.