Just recently started playing Alien Arena for fun (free) on Ubuntu which is Quake II or Unreal Tournament. AA is available for Windows, Linux and FreeBSD. However, I found that after upgrading to Ubuntu Lucid 10 that the audio no longer functioned. Open up Synaptic Package Manager and see if "libopenal1" is installed. Installing the Open Audio Library packaged fixed the issue for me. See you on AA.