Airset Online Organizer
Airset is an online web service that lets you organize things; it is basically an online organizer with sync functionality.
Update: Airset is no longer available. You may use alternatives such as Google Calendar or the Calendar app that comes with Windows instead.
It lets you create groups like work, family and gym online each with its own group members, calendar, blog, file sharing possibilities and more. Groups are color coded and can be viewed using a tabbed interface at the top of the Airset website.
Viewing a single group only displays the calendar and other functions of this group giving you a clean overview of what is happening there. The gym group for instance would display your sessions as well as those of the other group members which are most often close friends of yours.
If one group member edits the calendar or contact list it becomes immediately available for anyone else in that group as well keeping you up to date of coming events.
Then there is the All Groups tab which is a merger of all information from all of your groups. The calendar for instance displays all events of all calendars of the individual groups. These events are color coded reflecting the tabbed colors of the groups. It is possible to filter those lists to only display events that you take part in.
What makes Airset stick out from many of the other online organizers is the ability to sync the contents with Microsoft Outlook, a smart phone or Palm. It is possible to import your calendar (ical format) from Outlook into Airset for instance.
Airset is a free service that does not charge the user unless he would like to sync information with his mobile phone. I was not able to figure out how much this costs though. I suppose you could also export the information to Outlook and use Outlook to sync with your mobile phone instead without having to pay for it.