This site offers an unbiased price guide. It helps you track prices by offering price trend graphs. It will also help you shop by giving a narrower search according to your answers to the questions it gives you. Pretty much between Pricewatch, and Pricescan, you WILL find the lowest price on an item.
This website also offers very low prices, but advertisers submit their prices to pricewatch, where as pricescan is unbiased, and does its own price hunting. Pricescan is sometimes slow to catch on to price changes though. My suggestion is visit both when looking to purchase electronics.