Free Kibble is a site that was started by a 12 year old girl to donate kibble to her local shelter through people answering pet trivia questions in much the same manner as the Free Rice site. Since its inception the program has expanded to include 11 shelters throughout the country. With enough participation I'm sure more will be added in the future.
You're only allowed to play once daily on each site (there's a cat food site as well), but you can have automatic email alerts sent to you to remind you to take 30 seconds and do a little good in the world for pets. Plus, as a huge added bonus, the Free Kibble sites are partnered with Castor & Pollux, a truly great pet food company, to provide the donated food.
C'mon...30 seconds a day, tops. What could be easier?