A gold star goes to Domino's Australia (the pizza chain) for their twitter account. You see, most companies who get on to social media basically think of it as yet another one-way medium to broadcast hopeful messages to the already-faithful.
Domino's Pizza Enterprises (and a few others) do something that I actually appreciate: They actually communicate and converse. Sure, some of the tweets are just fluff, but they respond when addressed, answer questions, they provide a point-of-contact for complaints, and whoever it is at the keyboard makes an effort to advocate within the business for the people who have had problems or bad experiences.
That's pleasantly refreshing, and if you're doing that, you've got my interest and quite possibly my attention as well.