One are where there is a market from the consumer perspective but not much from the advertiser/business perspective is automated comparison shopping. As a result, there are not a lot of valuable sites that perform this function and they are all almost entirely automated. Froogle is one example and Savings.com is another.
Savings.com particularly shines when it comes to finding coupons for items you were going to buy anyway. It's like finding free money.
They are branching out into mortgage refinancings as well. To the latter, I can't attest as to their service, but their rates look highly competitive. If you're in the market, give them a try.
Update: OK, apparently all of those (aff) links go to the debt consolidation or refinancing pages. Boo. Stupid affiliate links. Here's a direct Savings.com link.
