One way to get great coupons is to join Manufacturer Newsletter programs.  If there is a product you like check out their website to see if they have one and sign up.  Many send out coupons each time or at least every other newsletter!

One I have mentioned before is Right at Home.  They send coupons on a regular basis and they also have great giveaways that are open to the first 10,000 each time.  With their newsletter you find out first!

A few others that are worth signing up for:

Nestle products (the only way to get to their printable coupons)
Kashi Community
Betty Crocker/Pillsbury
Marzetti products
Procter and Gamble

(one tip: get a free email account to give out to all coupon related sites so that these newsletters and anything else does not clog up your personal email)