There are many interesting Web 2.0 , AJAX sites.

Wow, Web 2.0 technologies are so amazing!

The Best Web 2.0 Software of 2005 by Dion Hinchcliffe
http://web2.wsj2.com/the_best_web_20_software_of_2005.htm

Here is another site contains list of popular AJAX app.
http://www.aventureforth.com/?p=13

Cool AJAX Site Index
http://ajaxmatters.com