A Yelp clone in Rails, with such illustrious features as Bing Maps integration, user comments and ratings, image uploading, user authentication, automated email notification messages and user dashboards.
The lessons actually have one small bug that you could look into fixing. Here's how to trigger it:
First create a comment for a place
Then destroy the place that's connected to the comment
Then visit your user dashboard.
Boom. It should blow up. This is because old items are left in the comment table that don't make sense, and then when looping through the comments, comment.place.name will blow up, because place will be nil.
Investigating using 'dependent destroy' on the association to fix it, to the comments connected to a place are automatically removed when the place itself is removed. You should be able to find some blog post that details how to do that.