I enjoyed browsing the Web 2.0 award winners. There are many interesting sites some that I have never even heard of. First off, I though Last-fm was amazing. It is kind of like Pandora (see Pandora post) but it has options to watch videos and talk with others about your favorite music. Since I am a huge music lover, I signed myself up right away. I also liked LuLu which is a self-publishing site. This is for all of us who are planning on writing a book someday (at least I know I am). I saw an old friend in the awards list, PBwiki. I can remember using this with a group of classmates for a class assignment. I was so much easier than e-mail files back and forth.
If I were to pick a site that could be useful for a library it would be WuFoo. It helps you design online surveys. Not only that but it organizes and analyses your data, creates reports and builds graphs. This would be a useful tool for a school library (taking a survey on what new technologies the students would like to see in there schools) or a public library (what type of book discussion interest you). I was a psychology major and I know how time consuming and sometimes mind boggling raw data can be. This site does everything for you.
I tried to sign up with library 2.0 and classroom 2.0 but they have to approve me first. The amount of info they wanted was impressive. I guess they don't let just and rift raft on their Ning.