Adobe's Flash is a program I have tried, but never really, got very far with it. Some sites are just plain stunning or highly ingenuitive. Some you wanna cry out "Why?" (damn those long intros without skip buttons).
Having said that I know there is a heck of alot that that Flash can do, i've see it and been inspired by it. One site that i like to go to is Vector Junkie, by James Hay. On this site there is a certain page that i like to visit just to see whats new. Thats the Experiments. There are some pretty cool things that can be done here and I recommened people have a look just to see what can be done with Flash.