I’ve just added it to my The Best Ways To Create Online Tests.
I was also considering creating a “The Best Ways To Create Online Flashcards” list, but, after looking over all the sites I know of and comparing them to ProProfs, I think ProProfs is definitely the place to go for flashcards, too. So I don’t think I’ll be making that “The Best…” list for awhile, at least.
However, I still have hopes that a flashcard site will incorporate being able to record audio someday. I’ll probably take the time to make that list when I find one with that capability.