Tower defense fans could probably spend the rest of their lives at http://www.towerdefence.net/
I played a few of them and they were pretty much the deepest tower defense games I've ever played. Some are RPG style with tonnes of items that give stat bonuses and everything. Worth a look if you like that kind of stuff.
Also I remember fantastic contraption
being one of the most entertaining flash games I had played.
And I remember someone posted a really cool flash basketball game where you basically shoot from all over the court but I don't remember where that was.