I'm taking CS50 through edX. Is it possible to have a pset regraded after it was graded once?
Yes, you can submit as many times as you need/want to up until the 31 Dec 2014 deadline.
Be sure if you resubmit, that you submit all of the programs for that pset, as they are graded as a whole. (In other words, if you need to resubmit
greedy.c, you should still submit
mario.c with it at the same time.)