If you're a fan of the Firefox web browser then there's a good chance that you'll like Sunbird which has been made by the same developer, Mozilla.
Unfortunately, not all of Mozilla's software is as good as Firefox but Sunbird is still a worthwhile cross-platform calendar application that's built upon Mozilla's XUL language. Note that Sunbird is still very much a work in progress and as such, even the name of the application could change soon according to Mozilla.
The interface of Mozilla Sunbird is very simple. Adding an event simply involves clicking on the 'Add Event' box in the top left-hand corner. The same goes for New Tasks. There's also a powerful search tool that finds events by keyword. Like most of Mozilla's products, it also seems very safe and allows you to set a password to access it. You can also extend Sunbird with a series of free add-ons from the Sunbird site.
On the downside, Sunbird doesn't feature integration with either iCal or Google Calendar, which you'd expect as standard really. You can, however, export the calendar. It also doesn't seem to be updated very often and looks like that Mozilla have put it on the back-burner for now.
However, if you use both Firefox and Mozilla's e-mail client Thunderbird, Sunbird is an ideal calendar component although most would probably be better sticking to Outlook's calendar.
