they are chock full of flash games and other webpage based mini-games. Good stuff there to, there are some that I've been addicted to when I'm bored at work. Heck theres even an option to have the game in an HTML Format just in case you wanted to stick it on your myspace or facebook or whatever.
I'm a huge fan of the VISA slap shot game that was on miniclip. Same thing with the Original monster truck game. There was also this penguin game that they were trying to sell, it was pretty cool I played it for a bit but eventually got burned out.
If you like point & click games, there's Mysteries of Time and Space (AKA MOTAS). Has around 19 rooms so far, and the creator keeps adding to it every so often. And if you fancy going insane due to a puzzle overload, you can try notpr0n. Largest web-based puzzle there is, and if you complete it without using hints (because apparently, the majority of hint websites are there to trap you), you get a certificate of some sort.