Go here to request a coupon for a free cup of Yoplait yogurt.
Many states will receive a free cup with no purchase necessary, but some states have ridiculous dairy laws which prevent them from being able to send you a coupon for a free cup. California is one of those states, so I got a coupon for a free cup when you buy 2 cups. That's still great with me, since I buy them 10 at a time!
Coupons.com has a $0.40/6 cups coupon (zip 90210, first page under "food" tab) that you can use with the free coupon to make for a nice deal if you want more than just one cup.