Go to google and type in armagetron. it is the first or second link. We grabbed the development version which was a little tweaky; however, there was a stable version. I think the main problems were:
A) If you're not playing on the server, then the last handfull of packets in a game are dropped, so funny stuff happens
B) If you're not on the server, you miss out on the entire first match - it doesn't let the server wait for players.
There is also a dedicated server, which would be cool to setup. It's tiny and fun.
If we had a dedicated server out there, I could play from work. :)