Keeping up with social media is an entire industry in and of itself (see Mashable).
The following social media cheat sheet created by Flowtown and Column Five media for social media sites was created for small businesses, but can be useful for teachers just discovering the joys–and pains– of twitter, facebook, YouTube, Google+, tumblr, and digg, among others. (Pinterest, for example.)
You are now free to connect with learners, find great content, and grow your professional learning community.
Infographic source Flowtown and Column Five Media; Social Media Cheat Sheet For Teachers (And Other Bipeds)