I ran MHR for a one-shot just fine using chatchyourhare.com's dieroller and Skype. The combination of text chat, VOIP, and a visual die-roller made the game work pretty well; the one issue is that assembling dice-pools is slowed, since you can't simply show the die as you pick it up.
Note that the catchyourhare die roller is graphical, and allows creating and dragging text labels (unfortunately, the labels are not governed by the color selector), dragging rolled dice around, and deleting individual dice. It's shared, as well - an entire group sees the same dice environment.
While it doesn't do tokens, per se, the moveable text labels make it quite possible to use names on labels and move them side to side to indicate who's gone this turn, and drama points, but that can result in clutter.
Note that the ability to roll the dice and create labels works on tablets, too, but doesn't drag properly on my tablet. In Chrome, long press the die, click away from the popup dialog, click where you want it. In Android Internet, one can't drag at all, but it does display.
Laptops and Desktops
I've used it in IE for Windows XP and Windows 7, and Chrome for Mac.
Skype is, in case one is unaware, a combined text and voice chat program. without charge, it supports text chat with up to at least 3 other users in a single chat, and voice chat for up to 3 additional users.
It does support group video chat as a paid feature; I've not used group video chat recently.
It also supports file transfers in text chat, which means prepared visual aids and character profiles can easily be transferred.