Check out web 2.0
Dave's new site: ROLLYO.
Web 2, in my opinion is the junction of:
1. large scale audiences with high bandwidth
2. no need to explain what you're doing
3. lots of tools you can use to build your app so you don't need a big team
4. user generated content
5. platform orientation
(note, it's not just #4).
Tip: to be #1 (check out the most popular rollyo on the site) it helps to go first! I'll never have a shot once it gets crowded.