I've been using the CouponMom "stack your coupons" system and have been making a real dent in my grocery and drugstore bills. I'll make a full report soon, but with combining store specials, 2-for-1 deals and manufacturers' coupons, I'd estimate I've saved $50-$80 this past week.
One of the big secrets of the CouponMom system is you save all the newspaper coupon circulars for each Sunday in a box, then the couponmom.com site alerts you to when grocery and other store deals match up with those coupons, so you can "stack" your coupons and get the most off for a purchase.
Also, I wanted to mention another coupon site someone suggested to me a while back: http://www.webbyplanet.com/ (WEBBY planet). You can search for coupons on all sorts of stuff from one search box.