Here is a couple of good flash sites that I have been enjoying of late. The first is a games site:
http://www.yetisports.org
I think its quite famous now, so its possible you will have heard of it.

The second is run by a mate of mine, and has made tons of flash animations and a few games. They all follow a story line, so its worth going in and starting with the first. Its up to you though!

http://www.matazone.co.uk