About two years ago I bought a new laptop. I wanted a unix without messing around with drivers for graphics and wireless, so I choose a Apple iBook with OS X. I havn't regretted but the inflexibilities of Apples user interface is a burden. So I'm playing with installing Debian on a Firewire-drive.
The installation (etch debian-installer RC2) worked fine until the installation of yaboot (the lilo and grub equivalent on powerpc). Google knew the solution: http://howtoforge.org/boot_debian_from_external_firewire (not really, Google found the same howto somewhere else). Problem number two was network: My wireless uses WPA-PSK and I don't have a free cabled connection. More googling: wpa_supplicant was the solution but it wasn't on the netinstall cd. Boot into OS X and download wpa_supplicant and some other usefull packages. Problem solved.
So now I have a firewire-drive with a pretty basic Debian install with X11 running. But I actually used 2 Apple applications (Safari and iTunes) and 2 other pieces of Apple hardware (iPod and Airport Express).
Safari is a minor problem, I just have to convince myself that my banking is just as (un)suportted with Firefox as it is with Safari. More interesting is the iTunes/iPod/Airport Express problems. iTunes is easily replaced by xmms but I really likes playing music through AirTunes and I need to keep my iPod updated. So it will porbally take some nore evenings to get completely rid of OS X.
And the I need two more mouse buttons...
Update 2007-04-16: Changed link to boborosso's howto as requested in the comments.