Arm & Hammer is giving away a free wildflower seed card to the first 155,000 people to sign up. They're only at 85,000 right now, so you've got a little time.
Seed cards are basically biodegradable business cards with little seeds in them. You then plant the card, the paper breaks down into plant nourishment through a complicated process that one scientist referred to as “no comment Goob, stop calling my home phone,” and then a few months later you've got a free plant!
You might have to copy and paste the link for it to work, so here ya go.
Your free seed card should arrive in 4-6 weeks.