I'm running a campaign using OpenRPG at the moment.
I wouldn't pay for online tabletop software, even if like fantasyground it has realistically physics modelled dice and pretty sheets. They're never going to actually replicate properly being there (unless they incorporate video-conferencing and such... maybe later, eh?), so I prefer the free option. It tends to be that the people you find are usually okay at typing, but do expect everything to take twice as long.
OpenRPG can set up a server on a lan fairly easily also, and isn't limited by cost to only one person GMing or by specific games. On the other hand, the miniature map leaves much to be desired. It's a functional program, but hardly pretty.
Never tried voice-based things, they might work, but at present I'm happy with text.