I do not use twitter in my own class, but many of my administrators and district professionals do. I think it's cool how many of them view twitter as a valuable way to share PD and other insights. Although I did not have a twitter before this class. I would often visit when they post and check out the different links that they have shared.
Some accounts that I like include:
https://twitter.com/senorfolsom (my school's instructional coach)
https://twitter.com/kirkjjohnson (my current administrator)
https://twitter.com/gatesfoundation (The Gates Foundation, focus on equity and how poverty can impact education)
https://twitter.com/HISTORY (History channel, fun facts to check out daily)
https://twitter.com/icivics (iCivics, government and History based information, as well as access to lessons to use with students in calss.