Calamander is the first innovation in calendar synchronization I've seen in a long time. Listen to Calendar Swamp podcast #11 (34:15, 64MB) with Calamander co-founders Scott Sikora and Derek Robbecke. And check out the Calamander beta. (Unless you have an iPad. The Calamander beta currently requires Flash, which the iPad doesn't support.)
My conversation with Scott and Derek arose out of my previous post here, which concerned Dipity, as Calamander implements its own innovative and welcome timeline view of multiple schedules.
After a long drought of no progress on calendar sharing, a flood may be coming. On Friday I attended the intriguing Inbox Love conference, where calendaring came up several times, most notably during a presentation on AwayFind.
Also, this week rumor has it that Apple will announce a refresh of MobileMe. When I talked with Scott and Derek on February 10, little was known of this so we were mostly bemoaning the continuing lack of a MobileMe API. Perhaps that is about to change.