I was doing a search on Wisconsin on one of the blogs and realized the University of Wisconsin was using this email collaboration suite, Zimbra. It looks as though it has been purchased by Yahoo. This open source project handles many features using AJAX and provides many advantages over traditional email clients. The back end makes it even more interesting. I have been using Gmail, but I question it’s security so I may be giving this a try.
Check it out for yourself: http://www.zimbra.com/