Depends on what content you're looking for, but off the top of my head, here's a variety of type of EM-related people/accounts. The first two are teaching resources. The rest are active (both clinically and on Twitter) clinicians or EM-focused students.

@emcrit

@epmonthly

@MDaware

@precordialthump

@seth_kelly

@mcsassymd

anything tagged #FOAMed (Free Open Access Medical education – often has an EM focus)