I've heard some positive reviews about gather.town[0] for virtual co-working, though I've never used it. The demos look cool though. It lacks the creative element of Minecraft though. I'm not sure to what extend the worlds are customizable. Curious if anyone has used it and has an opinion.
I've tried FocusMate, though that is along the "match-making" model, and I didn't get much out of a random pairing for 1 hour at a time.