Some people use maptools (although I'm not sure how well it supports 4th edition), some people use Fantasy Grounds.
It's actually MapTool not MapTools if you go to look for it, but you won't have to because here's a link to the site: RPTools - Home
I'm using MapTool and InitiativeTool at the game table (and both with TokenTool during prep) and I'm very happy with it. There are some issues but they can be tolerated.
MapTool I will probably continue to use, I'll write my own encounter handler to replace InitiativeTool eventually.
Huh. I never noticed that. Crazy.
The later builds of MapTool (I think around b45, but I know for sure b48, 49 and 50 have it) have an initiative tool built in to the program. I believe it's based off of the InitiativeTool (I don't see why it wouldn't be).
Really? Cool, I'll have to update my version. I'd love it to be a little more holistic as opposed to switching apps.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.