Low-latency, high-quality voice communication for gamers. Includes game linking, so voice from other players comes from the direction of their characters, and has echo cancellation so the sound from your loudspeakers won't be audible to other players.
Mumble, the low-latency VoIP application for games, has just released version 1.1.3. The files can be downloaded from https://sourceforge.net/project/showfiles.php?group_id=147372.
This should be the release that ends up in Ubuntu Hardy Heron, meaning Ubuntu users will have Mumble in their default repositories.