Many store websites have coupons available.  For example, Walgreens, Target, and Meijer all have store coupons (stackable with manufacturer coupons) available on their websites.  Walgreens' and Target's are printable coupons, and Meijers are called M-Perks which are loaded digitally by using your cell phone number.

There are also printable coupon websites all over the internet.  Some of the most popular ones include:

Coupons.com

Redplum

SmartSource

Coupon Mom

If you create a log-on ID for Coupon Mom, you can search the coupon data base for coupons and browse store deals which will help you pair up coupons with store sales to get the best deals.  Weekly ads can also usually be found on a store's website.