Ultrashock is one of those sites whose forums I tend to stumble around quite frequently on the 'net - but I've only recently taken a good look at it. The site itself is pretty impressive you know. It's mostly full browser flash, and a few of the interface elements gives away that it's based in Flex, presumably with some very custom UI elements.
There's the whole SWFAddress deeplinking going on, Flash and Flex integration, and a very seamless transition to non-Flash elements, like the Forums and Wordpress powered blog. If you're looking for a showcase Flex site, here's a goodie. FWA thinks so too.
What's more they're in the trade of selling content, kinda like FlashDen - which is cool.