I would suggest my readers check out this article by Tim O'Reilly. Though it is a bit dated (09/30/2005) it does a great job of describing Web 2.0. Mr. O'Reilly's detailed analysis of the changes a foot in content and design is at he heart of new Web pages by Yahoo! (go to the new design page). Online travel has a long way to go to truly capture the Web 2.0 movement. The key themes need to be collaboration, user generated content and aggregation of multiple sources of data. Most of the major sites have not changed in any radical way to address this trend and thus have opened the door for new applications that harness these Web 2.0 capabilities.