So, I've been playing around with the Google App Engine (when I have free time... yeah right!). I took their sample Guestbook app and added some data storage. Then I wondered how hard it would be to wire it into Facebook as an app. Spent about 10 minutes google'ing, tried setting it up and everything worked - that was too easy. Tweeked the page so it looked good, tried to get Google Analytics setup -- apparently it doesn't play nice with Facebook.
Anyway, check it out, leave your comment, and let me know what you think.
http://apps.facebook.com/publicjournal/