Installation on a MacBook is one of the features of Fedora Core 6
. I'm sure other distributions are planning to accomodate the machine as well.
My understanding of the implementation is that you tell BootCamp that you are installing Windows, but then proceed with the Linux installation. BootCamp then allows you to select which OS you will boot.
Alternatively, if you primarily use OSX and occassionally use Linux, you can run Linux under Parallels
. Since this is virtualization (not emulation, as the CPU is x86), performance is very good. The only thing to plan for in that case is sufficient RAM to run both OSX and Linux at the same time (1GB+).