XQF is a GTK+ frontend for Qstat, a tool for querying first-person action game servers like Quake, Unreal Tournament, etc. It displays information about the servers and allows configuring and launching some of the games from it.
Simply WOW! Did not expect server browser on linux for such an old games. I'm using it for Quake 2 with q2pro client and added my favourite servers from q2servers.com. Works like a charm, highly recommended!