I've transferred gimmie (and python-libgmail which it requires) to GNOME:Community this morning. I've not managed to test adding it to default.session so it contains a hacky script to start it with a basic GNOME session.

Would default.session work for users with an existing GNOME session saved anyway?

(I have tested replacing gnome-panel with gimmie in ~/.gnome2/session and that worked fairly nicely)