I've tested out ScreenMonkey and MapTool over the past month, but I haven't run anything with either. SM is easy to use and requires the players only use their browsers. However, it's $35 (for the GM/host only) and has somewhat limited capabilities. MT has a lot more options and is free, but everyone has to download the program (the same version, no less) and it's a lot more fiddly to use. In both cases, the GM runs his computer as a server that the players log on to,
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