AmazonWatcher is a nice little utility that will alert you whenever an out-of-stock item is once again available. It will also alert you about price drops - Amazon's policy states that they will pay the difference if an item you purchased drops in price within 30 days of when you bought it. Also, if you have an account set up with Amazon complete with billing info and a credit card, you can use AmazonWatcher to automatically purchase an item when it becomes availble.