Ask your neighbors who get the weekend paper if they would pass along the coupons they aren't going to use so you can start building up a supply. I'm always amazed by the number of people that get the paper but don't even look at the coupons and stick them in the recycle bag.
Roberta that is a good idea. My neighbor is elderly, and she and her friends in the neighborhood, each get a subscription to a different newspaper. And I get the Sunday Philadelphia Inquirer. I pass the Inquirer to her, and in return she gives me the coupon inserts from all the papers she reads. Neither she nor her neighbors use coupons, so I get them all. In return, whenever there are coupons in the paper for "free" items, I make sure she gets one - like the Oust plug in something or other last year. She had never heard of the product, and was thrilled that I actually took the time to pick one up (I got abotu 7 for my yard sale, so no big deal, not out of my way) for her.
Bus, train, and airports are also places to get extra inserts on Sundays. Just go pick up all the papers travelers have left, take out the inserts, and straighten them up, and leave them again for someone else to read. I have a friend who has a friend who does that, and then brings the inserts to her. The gentleman who does this doesn't have any money skills, can't read, etc. so my friend takes his monthly check, pays his bills, and often times has to physically go with him to buy food, and she uses some of those coupon in that direction for him.
If you live near a "recycling" station (ours is picked up every other week so I have any real idea about these) you can go there and see if they allow you to go through the paper recycling and take the coupons. I have heard this can be very lucrative, as some people take the coupons and re-sell them on e-bay.