Here are a few funny and crazy ways I have heard to get extra coupons -
Dumpster diving - yes I have actually heard of people getting into the recycling newspaper bins on Mondays or Tuesdays to go after lots of coupons people throw away.
Ask your neighbors - If your neighbors get the Sunday paper, you could always ask them for their leftovers.
Family members - my mom mails me her coupons every week. get family members to donate theirs to you.
Church or co-workers - ask around to see if people are willing to bring you their coupons
Local newspaper - go to the local office of your newspaper delivery and ask what they do with extras. sometimes you can make an arrangement to get extra inserts. taking donuts always helps.
Freecycle - I recently joined a freecycle group in my area. yesterday a lady offered a bag of uncut coupons for free. I was the first person to respond and picked them up
Buying coupons - yes sometimes it pays to buy coupons. if you know of a great sale coming up and really want to stock up, buying coupons is the way to go. Ebay has coupon sellers but my favorite is a company called thecouponclippers.com . they are quick and cheap. I've ordered several times and have been very pleased