Welcome to LQ.
The Yellowdog site has a list of all the hardware it caters for - I'm not a Mac person myself, so I don't know how complete this list is. As for the other Macs, are they PPC or M68k? You can still put Linux on the M68k Macs, but I believe it is harder to do... I'm gonna give that a go myself in the (probably quite distant) future.