|http://www.streetprices.com/ is a nice website that shows historic HIGH on LOW prices for a product you are planning to buy. So you can decide to wait or buy!!|
I have taken Garmin Nuvi 255W as an example. See the historic prices graph , they help you decide how low it has been sold in the past,that helps you decide the prices you are paying is a "GOOD DEAL" or not. PLUS it lists all retailers and compares their current prices as well.