http://www.iams.com/iams/feed-pets.jsp

Dear Pet Lover,

Our Feed Pets in Need program donates an entire month of free, dry pet food to your favorite animal shelter. All you have to do is vote. The shelter with the most votes wins, but the real winners are the needy pets who will be getting the quality nutrition of an Iams® diet.
Even though participating shelters can win only once a year, you can vote every day. Start helping us help them in three simple steps. It takes just a minute or two...really.

Select the state where the shelter is located.
Choose the specific shelter from the list we've provided.
Cast your vote.
Done!!! That is, until tomorrow when you can vote again.

Take a look at the program's Terms and Conditions and then sign in to find participating shelters near you.