Probably the most famous Ajax application currently available is the formidable GOOGLE MAPS.
View any maps of any location using Google's database of maps and satellite images. As you zoom and pan around the globe, Google Maps is quietly retrieveing map data from the Google Server. Impressive stuff.

WEBOGGLE is a challenging word game using Ajax techniques. Play against others online in real time, and see how you score. The site also includes an insightful account of how and why the game was developed.

And more to come ....