I gave a two day workshop on User Experience best practices in Web 2.0 at Gallup (yes, the polling organization) in Omaha last week.
Here's a slide from the seminar I thought you might find interesting capturing Usability 2.0 (whatever that is). It is a take on the infamous O'Reilly diagram capturing Web 2.0 concepts. My favorite is"iphone like magic" because I have had clients asking for web applications with that description.
BTW, my definition of Web 2.0 for the Gallup seminar audience was: