There are several web pages and blogs that can be useful in following the state of the art in GNU/Linux Games and in Free Games in general.
GNU/Linux Games
[http://www.happypenguin.org/ The Linux Game Tome] is probably the most relevant blog to follow. It's very up to date and updated quite often. It reports new games for Linux, new versions of games or information on software that might be relevant to games, like new versions of libraries and drivers. It covers Linux Games in general, not only Free Games.
[http://www.allegro.cc/ Allegro Game Developping Community Network] has also a few games using the allegro library, some working on Linux, some being Free.
Free Games
[http://freegamer.blogspot.com/ Free Gamer] is a commented compendium on Free Software Games.
[http://akaimbatman.intelligentblogger.com/wordpress/archives/27 Top 10 OSS Games You've Never Played].
"Sister" Projects
Well, not really, but the following projects fulfill a similar goal to the Debian Games Team, but for other Distributions:
[http://fedoraproject.org/wiki/Extras/SIGs/Games Fedoraproject Games Page]
[http://en.opensuse.org/Wishlist_Games OpenSuSE games wish list]
[http://www.gentoo.org/proj/en/desktop/games/index.xml The Gentoo Games Project]
Reverse engineering / free game engines
Other languages
(French) [http://jeuxlibres.net Jeux Libres point net]
(German) [http://www.holarse-linuxgaming.de/h2006/space/Open-Source-Spiele Holarse's OSS games list]
(Spanish) [http://www.linuxjuegos.com/ ?LinuxJuegos] is probably one of the most important blogs about games in Linux written in Spanish.
(Portuguese) http://www.ubuntugames.org/ - nice matrix of games, split by genre