I found this looking around for a few games to play today and it looks pretty good. It's an article with links to some great games, both browser games and freeware download games. It's split into several different categories and gives some great examples of different genres. I think a lot of the games have already been discussed here, but I saw some that I've never seen before that look interesting.
http://www.gamesradar.com/f/the-best-free-games-to-play-this-holiday/a-200812091054793016/p-2