This is just a quick tip in case you ever want to flash a mobile phone on gentoo.
If you look at the cyanogenmod howto  (in my case for a nexus s) you'll see that you need the tools "adb" and "fastboot" which usually comes with the android sdk. Naturally the howto suggests you to install this sdk, which isn't even available on gentoo.
However if you don't want java and all it's other dependencies on your computer (which is required for the sdk) there is package which installs only those two needed tools. It's called dev-util/android-tools - and it's in portage :)
This is all you need: