Shepard Fairey (@obeygiant)

Who: Street art god Shepard Fairey.

What to expect: Shepard Fairey's twitter isn't just a tool for self-promotion, but it's one for social activation as well. Fairey is particularly good as a not-so-overbearing pusher of art projects with a community push. There is, of course, the occasional plug for the Obey clothing line as well.