ZingSale is a free price tracking service that alerts you when something you want to buy goes on sale.

All you do is go to ZingSale.com, create a list of the products you are interested in buying, and within minutes, ZingSale begins tracking the price of those products from online merchants. As soon as a sale is found, you will automatically receive an email alerting you to the price drop. To make life even easier, the email alert also contains a link to the store where you can purchase the item at the sale price. No need to go to the store or hunt down coupon codes. It's an easy way to save time, while still making sure you're getting the best deals when shopping online.

ZingSale is completely free to use, and you can create as many price alerts as you'd like.