The Gentoo page in the wiki can be cleaned up a little.
A warning concerning the crossdev section: The current version of crossdev, 0.9.17 (binary is called crossdev-stable!) doesn't want to compile avr-g++ at all. I don't know why, but for avr, crossdev is set to always emerge to a stage without g++ which arduino needs. Comment out STAGE= in /usr/bin/crossdev-stable line 106 and you should hopefully be fine. YMMV.
Thats easily fixed without editing any files. Just run crossdev -t avr -s4 instead of crossdev -t avr
Also the ln -s line doesnt specify what the current directory should be.
I'm trying to figure that bit out at the moment.
So who else here uses Gentoo?
I'll use this thread as a little notepad to keep track of things to improve on.