P.K.
I don't personally use them, (bad habit and I should) but I've heard that you can get them at places like this: http://couponfrog.com/
I've also been told...as a tip, that it's only cost effective if you save money on the things you buy. Meaning, if you get a coupon...don't just buy the thing to get the deal. You're supposed to use coupons on stuff in which you already purchase...like the butter you buy, cereal, etc...and if you already buy it and it's part of your regular shopping trip, look for coupons on that stuff and use those that that's where you'll save money.
Buying new things generally isn't a money saver, even if it's on sale.