Plans, the best web calendar.
Users say:
I've been using plans for a month or two to synchronize social schedules among 50+ people, and I'd like to compliment you for the excellent work you've done.

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.)