A few years ago I put a bunch of games and activities on the internet (all free to use). The design of the site looks embarrassingly awful now, but many of the activities were first used with teenagers, and should work OK. It's
http://www.eltgames.com. There are lots of other sites out there, but the problem can be judging which games and activities will actually work with your students and which will bomb. Why not make your own? You'll be the best judge of what will work for your class, and it doesn't take long to knock something together and print it out. That's how I started, and now I make my living as an ESL writer.