I have found two alternatives to tossing out old coupons:
1) Walmart accepts coupons 3 weeks past their expiration date! Sweet!! =)
2) Mail them to "Coups for Troops" and from there, this organization will send expired coupons (up to 6 months expired) to troops overseas for them and their families to use.
The mailing information is:
Coups for Troops
PO Box 147
Winnabow, NC 28479