I'm fairly new to the mapping world. I run a number of modern campaign rpg's and want to stop drawing encounters on mats with wet erase markers.

My plan is to buy a pico projector and vertically mount it facing down, throwing the map image on to the table.

My main question is this: What software is best of modern map making? I want the 1" grid type maps. I own Photoshop CS3 and am a web developer by trade so have working knowledge of PS, but don't mind a mapping software do the work for me if there is a good one for modern settings.

I'm not too worried about the include image libraries as I will be importing much of my stuff as png's from various sources. Just need walls, windows, etc. to look modern.