If you play a "Zombie Mulch" game on Facebook, you can get a coupon for $5 off $5.01, $10 off $10.01, AND $15 off $15.01 at Home Depot. The coupons are good on lawn and garden products. You keep playing until you accumulate enough for each redemption level. They coupons don't expire until 12/31/12.
After you've hit each level, you can go into the "stats" page and request your coupon(s). I received an email about 10 min. after I requested it.
I had my kids play yesterday and, again, today. It seems to take about 20 min. for them to get to the next mark. (This can be less, if you follow the directions below.)
NOTE: Click on "Want More Mulch" at the top, before you start. It doubles the value of the zombies you're trying to "mulch" so you win faster. We started without doing that and it doesn't do anything if I click on it now, but after I requested my first $5 coupon (putting in my email address) they started doubling in value. Much faster!
I was a little skeptical about this and waited to post it, but it appears to be a legit coupon that they email. Nan has already redeemed a couple without any trouble. I'm excited about using ours!