I'm currently using Skype in conjunction with a program called YumiChat. It works ok, but this Fantasy Grounds program looks to be pretty nice. Only problem is, I don't have time to be writing a ruleset for it... and their forum pretty much forbids any mention of rulesets not of the d20 variety.

Does anyone know of any working sets?

Sorry, I've just been using Skype. I use a conference call and a text chat together. The text chat handles off-topic discussion, smart remarks, and large groups of dice rolls, and everything else is done over the conference call.
If there are maps for the session I either send them out when they ask for them our e-mail them out the day before as password-locked self-extracting archives.
I've toyed with the idea of getting a more functional virtual tabletop like Fantasy Grounds, but so far is hasn't been necessary.
YumiChat, huh? Interesting.
What functionality are you specifically looking for? It'll help us make better recommendations.

I've got an aborted SR4 ruleset Feshy and I were working on. It has a character sheet and some reference tables. PM me with your email address and I'll send it to you.

Well, YumiChat works really well for text chat and dice rolls, it has a great interface, and is really simple. It also has a rudimentary 'whiteboard' with generic tokens for mapping. From what I understand, though, Fantasy Grounds has an interface that allows drag and drop of images for sharing, along with just user-friendliness.

I'm probably going to end up using MapTools if FG doesn't look good. But in the end, most of this stuff is just icing, the system we're using works well enough.

BTW, thanks for the work you've already done, and for helping out, 2bit!