Linux gaming is a really popular topic right now thanks to SteamOS and Steam Machines, so I thought I'd gather some links for you guys.

Linux gaming subreddits:
http://www.reddit.com/r/linux_gaming/
http://www.reddit.com/r/SteamOS/
http://www.reddit.com/r/linux/ sometimes has some Linux gaming stuff too

Wikipedia article on Linux gaming:
http://en.wikipedia.org/wiki/Linux_gaming

List of Steam games available for (or coming to) Linux:
http://steamdb.info/linux/

Linux gaming website:
http://www.gamingonlinux.com
http://linux.softpedia.com/
http://rootgamer.com/

Feel free to add more