I'm looking to install Debian and Gentoo alongside Mac OS X on a (Intel) MacBook. Debian will be for using Linux, and Gentoo for toying around. There are lots of guides on the Internet about dual booting, but I haven't found any on triple booting two Linux distributions and Mac OS X...
I'm thinking something along the lines of using rEFIt and GRUB - but maybe only GRUB is the way to go.
What to do here?
Just get a copy of VirtualBox (it's free) and install your experimental stuff on that. You will use less aggregate disk space and the performance impact is minimal, especially for non-production uses.
The MintCast podcast just did an episode on Grub, which might be useful, but I would also go with virtualization, particularly if you are looking to try out multiple Linux dustributions. VirtualBox is free and quite good, but in the same situation I chose to use VMWare Fusion, as their web site has many "appliances" - prebuilt virtual machines with Linux and other OSs, which makes installation very quick.
I found an answer at http://wiki.debian.org/MacBook/DebianInstallTutorial
Thanks anyway ;-)