Kongregate

Kongregate is an online 'hub' for flash players and game developers to meet up, play games, and operate together as a community. Players are able to rate games which creates a nice 'digg' type buzz around the better games (Digg's playable webgames is another great resource for finding games).

Kongregate also has a number of forums, an online chat facility and the ubiquitous tagging of games.

Another great community for Flash game players and developers is gotoAndPlay(). If you wish to develop your own Flash games the tutorials on this site are particular good.