Basically you save your My Coke Rewards codes and enter them in for prizes and such. Some of the prizes are kind of cheezy and in my opinion nothing I would save like crazy for, and the ones that are really good have an astronomical point value. However my husband drinks an insane amount of Coke and we do save our rewards.
I turn mine in for coupons for free food or drink that they will snail mail you. You can also get free Club Pogo memberships by turning in your codes - my son enjoys this very much. Also, you can get the codes off of anything manufactured by CocaCola, including Powerade and Desani water, so it's not just Coke you have to drink.
The things I don't like are the site only allows you to enter 120 points a week which is kind of a pain in the butt...I like to enter whatever I have all at once and not have stuff hanging around my house...but it works for me I guess. And also if you don't turn in points or trade for a reward for 90 days your account is considered inactive and you will lose any points you have banked. I have a friend that this happened to, but she did say she called the company and they had great customer service and replaced her points for her. All in all, if you or someone in your house drinks a lot of Coke products, this is a decent site.