Ziipa is a "web 2.0" search engine that I found out about from Shelly Terrell's wonderful blog. This is unique among search engines because it only focuses on: Web 2.0, start-ups, and applications... ideal for the 21st Century educator!!
Another nice feature of Ziipa is that the results come back by showing a thumbnail of the site, w/ a star rating system that you can vote on. Features like these make searching for "web 2.0" tools a snap.
Below are results for a search on the term, file sharing.
Give Ziipa a try by clicking here.