A couple of the guys and myself at Appirio are writing a beginning Google App Engine with Java book to be released this fall. We've locked down the functionality of the app we are going to be discussing in the book but I would like to put the app out to everyone and get any feedback regarding the user interaction.
You can run the application at: http://book-timeentry.appspot.com
The use case is fairly simple. This is a time card application where users login with their Google credentials and enter time against a project and milestone. The user's time is persisted to BigTable and can be viewed by selecting the "Current Entries" tab.
Please let me know if you have any issues, recommendation or general feedback on functionality. This is a beginners level book so the app won't go into too much depth. Any feedback would be greatly appreciated.