I've mostly played D&D 3.5, so that's the one I'm most familiar with. I've also played some Pathfinder and Palladium games, but I still don't have a good grasp of Palladium. Other D&D experience has been limited to what I've played in some of the older computer games.
I've been looking into the Roll20 site more, and I'm currently trying to put together a complete campaign on here (covering levels 1-20). If all goes well, I'll be inviting people to play test the game and work out any kinks. This is probably going to be closer to a June or July thing based on my life outside of the gaming though.