Other handy features, such as private chat rooms, shared file storage, local weather forecasts and pager notification are available on many sites. There are easily two dozen calendars on the Internet. Like all Internet services, you should check a few to see which sites best suit your needs. The best sites offer secure connections. Even so, I wouldn't store company trade secrets on these sites, although individual calendars and to-do lists probably don't pose much of a risk.
All sites have privacy statements.
You want to make sure your definition of privacy matches theirs. These are fledgling enterprises. Some won't fly far. Make sure you can maintain your own copy by synchronizing or downloading your calendar or contact list. You don't want to have to file a claim with a bankruptcy court for your information, if your site falls into Chapter 7.