In no particular order, and those I find helpful and interesting. Some of these folks are friends and colleagues. Note that some accounts don't always tweet about national security - but when they do, they share interesting stories and perspectives.  Enjoy.

• @froomkin - Dan Froomkin now at the Intercept.
• @attackerman - Spencer Ackerman, formerly a reporter at the Danger Room blog at Wired, now at The Guardian. 
• @rhodes44 - Ben Rhodes, White House Deputy National Security Advisor for Strategic Communications & Speechwriting.
• @QWiktorowicz - Quintan Wiktorowicz, former White House official, entrepreneur

• @hoffman_bruce - Bruce Hoffmann, director of the Security Studies Program at Georgetown University's School of Foreign Service

• @StateDeptCT - U.S. Department of State Counterterrorism Bureau

• @CNSFordhamLaw - The Center on National Security at Fordham Law School. 

• @JessicaEStern - Author of Denial, Terror in the Name of God, The Ultimate Terrorists & other articles on terrorism; policy consultant and lecturer on counterterrorism and PTSD.

I'll add more from time to time. Do you have others to suggest? Let me know in the comments below.