Mars is sponsoring a Chocolate Relief Act every Friday through this summer. All you do is log in on Friday, be one of the 250,000 people that day to log in, and you'll receive a coupon in the mail for a free full-size Mars product (M&Ms, Snickers, Dove, Milky Way, Twix, 3 Musketeers) in a few weeks.
A blurb from the site-
Limit: one (1) Coupon per email address per Friday and four (4) Coupons per household during the Offer Period. Subject to verification of eligibility.
I will probably no longer be eligible since I've already gotten 3 of the coupons, haha.