Remember a couple days back when we recommended using Amazon's 30-day price drop policy to your advantage? We thought that was a pretty good idea, obviously, but keeping track of the price drops for every item—not just in a month, but every day in between—sounds like a real hassle.

Not so with Amazon Credits You, a free service that keeps track of your purchases for you. All you have to do is enter in your purchases—no personal information besides email required—and they'll send you an email if and when Amazon lowers the price. They'll even add a handy link in the email for letting you claim your refund from Amazon.

And although we think the Amazon Wish List would probably work almost as well for this, Amazon Credits You could also be used to keep track of price drops on items you haven't yet purchased, albeit only in a 30-day window. (Thanks, Fred!)