To date there are a few articles of note that I have read and recommend for further understanding of this new use of technologies:
- ASP.NET Spiced: AJAX by Karl Seguin published Sep 2005
- The above article points you to Michael Schwarz's Ajax.NET Professional download and samples page.
- Ajax: A New Approach to Web Applications - The man who coined the Ajax phrase or acronym, Jesse James Garrett, from Adaptive Path writes a very thoughtful and well thought out article describing the basics. Feb 2005
Some famous applications using Ajax technologies are Google Maps (drag and zoom without refreshing the entire page), Google's Blogger front page with a scrolling marquee