There are really only a few places to look and get these money savers.
1. Go straight to the manufacturer site. This can be time consuming, but you can not argue with the savings.
2. Smart Source. These are the same folks that bring you some of the Sunday coupon inserts every week. Smart Source also makes their coupons available for printing online. I use them to get free duplicates on the ones I need extras of.
3. Coupons.com is my favorite. The box directly after this post will lead you to some fantastic deals.
4. Amazon Grocery Coupon Codes. Of all the online grocery saving resources, Amazon has the best clearance sales and promotions. When the have products go on sale they reduce the price, offer free shipping, and then usually offer a huge 40% discount on top of that. Amazon grocery is a best kept secret for saving. Check the Amazon Grocery Specials Page
The reality is that regardless of what kind of grocery coupons online you are looking for online, knowing where to find them quickly and easily will save you a lot of time every week.