HipCal

Let's start with an online calendar service that I would not readily recommend - HipCal.  HipCal started off a couple of years ago with a lot of promise.  It has not only an online calendar but a task list as well.  It has a social aspect in that it allows you to create group calendars.  It has ical compatible export, and allows you to keep contacts on the site as well.  It has recurring events and reminders by e-mail or SMS.

Sounds great right?  Well let's get to the one big reason why I would not recommend it.  Development on HipCal has come to a complete halt.  The developers were hired by Plaxo to work on their online calendar, and HipCal has been abandoned.  It's still online, and still works well, but I personally don't want to put a lot of data into a service that may very well be gone tomorrow.  In fact, I'm surprised it's still online.  I expected it to be gone shortly after the developers announced their deal with Plaxo, because I assumed they wouldn't want another calendar service online competing with the one they're developing.  Over a year later, it's still here.  You can visit the blog and see that the last message was the Plaxo announcement, and the forums have been shut down to prevent spam.  One other minor gripe, the week view doesn't work in Firefox, even though it works fine in IE.  They promised to fix that, but the abandonment came before the repair did.

If you like it, use it, but buyer beware!