If you sign-in you'll see a leaderboard on the right. Citizen Radio has held the #1 position for a very long time. They have 841 Twitter donors and 498 Facebook donors. Their messages are constantly pegged to the top of Twitter search results for given hashtags and keywords.
A high school drama club setup this campaign linked to a Facebook page for a play they were putting on. They didn't end up using it but another interesting intent.