I enjoyed this short video about students using technology in their English class. While I have yet to incorporate Twitter into a lesson, it's something I'm open to trying. The National Council of Teachers of English has recommended that teachers begin working 21st century literacies into the classroom. The NCTE has also put together a policy brief for teachers and administrators about what 21st century literacies are, and what they look like in the classroom.
Here is one more video about using Twitter specifically in the classroom.