PUBLIC MARKS with tags bestof & ajax

Following are my picks for the 10 best Ajax applications. Selection criteria: (1) an appropriate combination of simplicity and rich functionality, (2) somehow compelling (hard to define, but I know it when I see it), (3) the more interactive, the better, and (4) free. Also, in this exercise, I’m focused on startups, so I’m not including anything from Google (maps, Suggest), Microsoft (Kahuna), or Yahoo (Flickr).