Twitter

Twitter ( http://twitter.com )  is a worldwide "real time information network" that limits posts to 140 characters.  Members are able to both post and view others' posts.  Posts appear instantly, can be repeated to others, and shared other various ways.  Twitter can be accessed by computer, game console, smartphone, and a variety of other ways, so it is constantly available.

placetofly's twitter feed of math questions and experts.

Advantages of Using Twitter to Teach Math

Because Twitter is a worldwide, highly saturated communication network, new information is constantly flowing into it.  This provides a fertile ground for new ideas, problems, and concepts to be posted and discussed.  Also, because the messages are limited in length, much information can be viewed in a short period of time, increasing efficiency.  Twitter is a resource for information that can be used to scaffold and create lessons, or use a classroom feed to allow students to seek out their own problems to solve.

Lessons that can use Twitter

NCTM, the Twitter account of the National Council of Teachers of Mathematics, has daily questions or exercises. 

TwitterVision - Follow Twitter users across the world - Geography lesson

50 Ways to User Twitter in Education

Twitter Math - Let Twitter itself be the lesson!

General Twitter Resources

Twitter4Teachers - A PBWorks Wiki specifically for use of Twitter in the classroom.