The first one I've known about for a little while now and you may have heard of it too but http://www.coupons.com/ is a great place to find coupons on good name brand household items. You can even save on things like your next visit to Sears Portrait Studio or Chuck E. Cheese's.
The next site, http://www.alice.com/ was shared with me by my co-worker just this week. From this site you can order various items at disount prices and there's no membership fee. They also compare prices to other sites and will keep track of what you have and find you coupons for what you buy.
Last but not least, I enjoy browsing http://www.dealcatcher.com/ just to see what kind of bargains are out there. It shows online sites like overstock but also shares deals from your regular brick and mortar's like Toys R Us and Macy's.
Hopefully this week was not too much like an infomercial and no I'm not getting paid for sharing this information with you (I wish!). I just love getting a good deal and paying nothing for something : )