Stacking coupons is a great idea. You can ask the grocery or gas/convenience store for the inserts sunday night- they only have to give the papers back, not the inserts and then you can get some awesome coupons for free. Or there are some really nice online sites that help couponers. http://www.southernsavers.com/ is one as an example.
You can also get a lot of free stuff out of the Walgreens register rewards program if you just take the time to look through coupons and the register rewards.