Buzzillions
Based on real buyer feedback, they help you find, compare, and decide on the right product. Users are guided to similar consumers by asking how they will use the product and what sort of consumer they are (”Getting Started, Casual User, Professional, etc..).

Kayak
Know when to fly - compares low airfares and shows when it is cheapest to fly. Many useful tools for narrowing down your search by price, time of day, and so on.

BugMeNot
BugMeNot.com was created as a mechanism to quickly bypass the login of web sites that require compulsory registration and/or the collection of personal/demographic information (such as the New York Times).

RetailMeNot
A catalog of online coupons posted and reviewed by users. The coupons vary from sites like JCrew to Amazon to ebay. And they have a nice Firefox plug in.

How Stuff Works
Pretty self explanatory.