On an Intel machine you have the choice of them all, with the limitation that some distros might not configure or easily configure all the devices in this Mac. For example, linux has problems with some wireless chips. Google, if you have not, for your machine by model number and linux. I use openSUSE which has I believe good device support for Mac. It is much a matter of having a new version of the kernel as the "drivers", in linux, moduls, are part of the kernel. openSUSE 11.1 is just released and would be a candidate.
There are so many linux distros and personal preferences are so different that the best standard reply is to burn some live-cds and try them out yourself.
Many will now jump in with their favorite, but you may skip on to the standard list.