SpongeCell is a new Ajax calendar built on the Ruby on Rails platform. In addition to the now-ubiquitous drag and drop interface, Spongecell is adding artificial intelligence aspects to turn natural language into structured calendar entries, and has a nice mobile interface. More information is here. Spongecell is having an open launch party on Wednesday, February 1, 2006 in San Francisco.
Ajax calendars are faily commonplace now (they are kissing cousins to Ajax home pages as far as I’m concerned) and seem to be breeding just as prolifically. My list now includes: