I've been using a mobile phone calendaring service for the last six months or so. It's really rather good because it integrates into the Nokia calendar I use on my Nokia 6630, and you can synchronize it with the web version. It's a lot easier to enter stuff in the web interface than on the phone, and the interface is better.

The SyncML interface means you can enter calendar entries from either place. So if you're sitting at your desk and someone sends you details of a party, you can add it right in. But if you're out and about, you can equally easily look up your availability and add a new item. Very cool.

The developers are very receptive to bug reports and feature requests. I found a bug with recurring events (specifically, Critical Mass which is last Friday of the month) and they responded and fixed it in a couple of weeks.

Apparently ical support is on the feature list for a near-future release. This would allow me to subscribe to various events from other websites. I'm thinking NSW public holidays and fixtures for Sydney FC and the Socceroos.

So all around, a very cool service. For those of you who require buzzword-compliance, the UI of the web stuff is suitably AJAXy.

I believe their business model is to sell the service to Telcos as an add-on for their customers. At the moment, and they claim forever into the future, it's free. Regardless, if they were to fold tomorrow you could always sync to another SyncML service from your phone as a migration path.