One question even I have at times is "Should I trust this Web site?" - for example, a while back, a Web site named ClubIT.com had a nice deal on a computer part I wanted, but I hadn't really heard of them.
One of the Web sites that people trust for accurate ratings of Web sites is Reseller Ratings. It's a site that's been around in one form or another for over ten years. You can check out just about any online retailer that you haven't heard of and see their ratings.
Direct link to their store search: http://www.resellerratings.com/store/
For example, you can see some of the Web sites that people have had a lot of problems include sites like buy.com (who I've personally had some issues with myself), and some of the best stores include newegg.com (an excellent computer retailer). People have the chance to write detailed ratings detailing their positive or negative experiences. Highly recommended, and free to visit and use!
The best and worst retailers @ Reseller Ratings: http://www.resellerratings.com/topstores.pl