Google Calendar, launched just a few days ago, is a service I see myself using extensively. The first thing that grabbed my attention is the typical (for Google) uncluttered and simplified interface. Google Calendar is powered by Ajax, a web technology that allows the updating chunks of information in a web page without having to reload the entire page itself. This makes adding and editing calendar entries easy and unobtrusive.
The interface is intuitive and adding an appointment is easier than writing an email, which should be the case. To add an entry, you simply click on the box beside the time in the day column and type the details. You are not forced to configure the event like set up reminders or enter such details as venue or attendees. You can configure these things only if you choose to do so.