Thanks to nfarina for a patch to improve compatibility with older IE versions.. jQuery UI AddToCal widget is stepped to 0.1.1 and now listed in the jQuery plugin store.
To recap .. use AddToCal if you want to offer your website visitors the ability to add any events you list or present on your site to their own calendar. It supports Google Calendar, Microsoft Live Calendar, Yahoo! Calendar, 30boxes, any iCal or vCalendar compatible desktop application (and you can extend it to support any special calendar software you might be dealing with).
See my previous post that describes how to use it in a bit more detail..