There are so many web2.0 web sites out there, it is impossible to know them all.
The directories help find new interesting web2.0 sites to explore and get inspired by.

A list of few interesting directories:

• http://web2.econsultant.com/
  Divided by categories

• http://www.go2web20.net/
  With colorful logos of each web 2.0 site

• http://www.allthingsweb2.com/
  Categorized by popularity, rating, reviews

• http://www.prelovac.com/vladimir/top-list-of-social-media-sites
  top 100 sorted by Alexa ranking

• http://bobstumpel.blogspot.com/
  Get RSS feed with links to web2.0 sites

• http://my.mashable.com/links/network
  Social network grid

I am sure there are more good directories, and will be happy to learn about them…

And finally my humble list of web2.0 sites and resources. The list is short and includes only sites that I like the most and sites that I plan to try out.