Are you owed a refund on your online purchase? do you check?

Well, you don't really need to anymore. Price protectr is a really great service, it tracks price changes in anything you might have bought from online stores that offer a price-drop guarantee. If the price drops, and you notice it, these stores offer to refund you the difference, but in almost all cases that is dependent on you asking for the refund.
Amazon, Costco, CircuitCity, Sears, Costco, Staples, Best Buy, and Staples are included, though the full list of stores they cover can be found here.