Mechwarriors, Descents, Freelancers - anything where your in game "avatar" isn't tied to the camera can benefit immensely from the technology.
You can buy the original games from gog.com and then download the updated clients for D1/D2 from http://www.dxx-rebirth.com/ or find the patches for D3 via the links at http://descentbb.net/viewtopic.php?f=1&t=4953 . There's a game tracker at http://www.descent-servers.net/ and built-in trackers in D1 and D2.
Some groups that are still active include http://descentrangers.com/Home/Index (primarily D2 and D1 team play), http://rbb.ripteam.com/ (D3 teams), and http://descentchampions.org/ (a 1v1 ladder for mostly D1).
You can find other Descent pilots on facebook at https://www.facebook.com/groups/descentpilots/ , https://www.facebook.com/groups/kalikahn/ , and https://www.facebook.com/groups/583400181716926/ .
Disclosure: I am one of the founders/administrators of the Descent Champions Ladder.
The Descent1/2 source is freely available, so some brave soul will probably add Rift support.
Coincidentally the second game I tried with it that day was Mechwarrior 2.