Basically,
Kongregate.com is my new favorite site. If a flash game is good, it's on Kongregate with a full chat system, achievements, and a metagame that ties into the site's online CCG.
But the important thing is GOOD flash games. There's a lot of stuff that kicks ass, for example:
Gemcraft- Basically the best tower defense game ever made. It's incredibly well done and addictive and so much better than basically any other TD game.
Chronotron - Puzzle platformer that makes genius use of time travel. What Blinx for the XBox should've been.
Sonny and
Monster's Den: Book of Dread - Both fantastic turn-based RPGs, with Monster's Den being a basic dungeon crawler and Sonny being the quest of an intelligent zombie to...uh...kill other zombies. They're nifty.
Dolphin Olympics 2 - The achievements make this game worth it. I spent basically 3 hours getting to the Restaurant at the End of the Universe. Fun, difficult game.
At any rate, any other Flash games worth playing out there, Kongregate or not?