Monket Calendar – Wiki – monket.net:

About

An Ajax enabled online calendar. Drag and drop events to change dates, drag the start/end of an event to create multi-day events, create and edit events without refreshing the page, all with an iCal style interface.

This release now works in all major browsers (Firefox, Opera, Safari, and Internet Explorer). IE support still has a few bugs, namely the previous/next month links not working, and the need to click on a multi-day event before you can resize it.