Plans, the best web calendar.
Users say:
I've tried many many types of calendar/pim software programs in the past for both Windows and Linux and for my requirements this is streets ahead of anything else I've tried.

Who uses Plans?

Plans is currently used by:

See what Google has to say.

Plans has an entry on Freshmeat, where some folks have posted comments.

TotalChoice Hosting has detailed instructions for running Plans on their servers.
(Disclaimer: has no business relationship with TotalChoice Hosting.)

(Disclaimer-er: In fact, has no business relationship at all. The ".com" is sort of misleading.)