What period are you looking at doing your campaign in ?
For straight out digital maps, I just use one of the overlay managers that sit on top of Google Maps / OpenStreet Map.
There is mapbox.com you can use there "pirate map" mode to create really excellent period flavour maps if you want.
There is also maps.stamen.com which has some excellent terrain relief overlays, and watercolor painting maps, where the tiles are generated on the fly to look like a painting or a real map.
For map / campaign management though, heres one I cooked up earlier that runs on ipad / android / browser, for Napoleonic gaming :
Allows for realistic ground scales, based on your figure and basing conventions, and then takes it from there to run a tabletop game.
Map view from a player's iphone, and an android handset as well :
The map integrates back to a full OOB editor, which includes all the usual stuff for each Corps, down to the Battalion level :
On the maps again, you can specify Objectives, which each get a label on the map, and they have a Victory Point setting .. like this :
And you can specify which "side of the table" each player is on, so all the map features get flipped upside down when viewed by the opposite player.
eg. here is a view from 2 different users on an iPad, one running the French (Red Force), and the other the Prussians (Blue Force)
Same map .. but flipped depending on which player is looking at it.
There is a lot more in there beyond the map side of things, including command and control, and a tabletop combat system as well.
