In simple words,
Web 2.0 sites are nothing but the sites which allows us to create blogs and to share them.
Use of Web 2.0 / Web 2 sites in SEOFew days ago I written an article on how to create an effective linkwheel
We can use Web 2.0 sites in our linkwheel to boost traffic to our money site dramatically.
Here is my huge Web 2.0 site list.