Tremulous 1.1/GPP/Mixed servers - they have multiprotocol servers, which means you can download new clients that are built for 1.2 GPP and still play on servers hosted by this group (at the moment, test7341, GrangerClub and GrangerPub). There is active development in the dark hidden room. Most of the players are living here at the moment.
http://discourse.grangerhub.comOpen sourced "Successor" of Tremulous GPP style gameplay, although their actual tactics and team play has changed significantly over the past two years (they don't use build point system, they have spikers similar to the one from Gloom etc.) though they severely lack a playerbase. They also require newer hardware as they use OpenGL 3 with 2.1 as the bare minimum, although it doesn't seem to work on my GL 2.1 system anymore due to lack of legacy hardware support. It's in alpha stages and is in active developement with monthly releases. Kharnov is willing to convert you from the kawaii granger religion to their world of bot servers.
http://unvanquished.netand if you're willing to go for paying and the lack of modification support and willing to wait for a game that hasn't been released for another 2 years or so mainly due to a disruption with the legal side relations to Tremulous in the past (they called themselves "Tremulous2" without asking all of the contributors to Tremulous, which is pretty much impossible now):
http://murnatan.com
