Learning web 2.0

I'm intrigued by Ajax, the technology behind Gmail, flikr, kayak, and gosh know what else. Ajax is the new technology of the era Web 2.0.  I've been setting sometimes now to learn about Web 2.0, so far not much progress. 

http://www.techsoup.org/toolkits/web2/ 

Today marks my real attempt to learn Web 2.0