If you're just getting comfortable with the concept of Web 2.0, hold onto your hats because Web 3.0 is here. But not to worry, Amit Agarwal explains the differences between Web 1.0, 2.0 and 3.0 in plain english on his Digital Information blog. He says: "Web 1.0 - That Geocities & Hotmail era was all about read-only content and static HTML websites. People preferred navigating the web through link directories of Yahoo! and dmoz.
Web 2.0 - This is about user-generated content and the read-write web. People are consuming as well as contributing information through blogs or sites like Flickr, YouTube, Digg, etc. The line dividing a consumer and content publisher is increasingly getting blurred in the Web 2.0 era.
Web 3.0 - This will be about semantic web (or the meaning of data), personalization (e.g. iGoogle), intelligent search and behavioral advertising among other things."