Price Protectr (YES, it's spelled like that...drives me crazy too) is a great site if you make a lot of online purchases. Lots of sites offer price matches if their price drops after you buy the item. The problem is that you have to check the site everyday to see if the price has dropped or not. And Amazon is famous for changing prices multiple times in one day so you'd never be able to keep up with that!
Enter Price Protectr. It watches the prices for you at 116 different stores and e-mails you if the price of your item drops before your time is up. It is so easy to use. I used this last fall when we bought our new TV off Amazon. We had to get several price adjustments but by the end of it all we had saved an additional $120. Woo-hoo!