Running a TeamSpeak client on Gentoo is quite easy. But there is only a binary available. Installing it is as easy running “emerge media-sound/teamspeak2-client-bin“.
The only problem I had, was that it was blocking the sound-card when it was running. Teamspeak worked fine with alsa, but no other program could use the sound-card at the same time. This makes it completely useless for using during games… This happens because teamspeak uses the old oss sound system, which only allows multiple programs using the sound-card if it has a hardware mixer. And my sound card has none. Alsa emulates it, but this apparently doesn’t work right.
To fix this do “emerge media-libs/alsa-oss” and then run “aoss teamspeak” instead. I found the solution here.