Couldn't you use Google Calendar for group calendaring? Just have everybody add the mygroup@gmail.com calendar as an overlay.

And folders are just a degenerate case of labels, where each message can only have one label. You can set up a filter to "label as emacs-devel and archive", and watch the unread count in the labels box. Just as easy as folders, though it's harder to have a "favorites" list like in Outlook.