We’ve been using Calcium, the web-based shared calendaring software from Brown Bear Software, for some time now. It works very well, especially for a distributed organisation like ours, and the support from the Brown Bear staff is superb.
Until recently, however, I couldn’t see my appointments except when connected to the net. Not really a problem – I’m almost always online. But the latest version allows me to access our calendars in iCalendar format, meaning that I can subscribe to them from Apple’s iCal. Now, not only do I have a (read-only) copy of the corporate calendar with me on my laptop, but also, through the magic of iSync, on my iPod. Very sweet!