Ajax in many ways is the basis for Web 2.0. The funny thing is that Ajax has been around long before the word web 2.0 was coined. Microsoft developed a Javascript function for Internet Explore 5 called XmlHttpRequest. This is the essence of Ajax. One single function which seems to have caused an overnight explosion of rich web-based applications.

Web 2.0 is based on this because Web 2.0 is highly interactive - similar to what you would find in a desktop application. Web 2.0 is about the rich user experience. No slow page loads or postbacks. Almost instant data and responses because most of the processing is performed on the client machine as opposed to the server (where most processing took place 5 years ago).

Google maps and Microsoft's LiveSearch both use a great deal of Ajax and web 2.0 methodologies. Another site with Ajax examples (the first one that showed up in search results) is http://www.ajaxdaddy.com/.

Marketpath CMS uses Ajax throughout the entire application on every page and every dialog. We could probably stretch all of our Ajax code from coast to coast in 12pt font.

Developing web-based applications with Ajax and web 2.0 methodologies is no longer cutting edge. It is a requirement for intutive, easy-to-use, and responsive user interaction.