Web2.0

Here is an nice article regarding web2.0 :
The term Web 2.0 shows up a lot in the on-line and in-print press when discussing some of the new web sites on the Internet. Places like Flickr, Blogspot, Wikipedia, 37Signals, and AjAXWrite are just a few web sites that embody the Web 2।0 paradigm.
Read More>> SciTech Watch - Web 2.0

Update:

Web 2.0 is the business revolution in the computer industry caused by the move to the internet as platform, and an attempt to understand the rules for success on that new platform. Chief among those rules is this: Build applications that harness network effects to get better the more people use them.

Another good explanatory article What is Web 2.0? Really.