Another option that might work for you if you have a the funds for it. I was once in a group (about 5 years back) whoes DM managed to get his hands on a digital projector. You know the kind that plugs into the back of your laptop or PC and is primarily used for meetings and presentations? Well what he did was take the projector and mount it above the gaming table facing down onto the table itself.
What he would do is take the maps he wanted to use, be it a home made map, or one he tore out of a Dungeon Magazine or a module and scan it into photoshop. He would then make a mask over the image that he scanned that covered the whole map with black (or whatever color he wanted to use to prevent it from being visable) He would then of course shoot the whole thing through the projector and onto the gaming table.
Through trial and error he was able to size the projection to where it had the 1X1 in grids to scale. As a party went through the dungeon, he woudl use the erase tool on photoshop to erase that part of the map thus showing the progress without giving away the whole map!
There are pros and cons to this idea though.
The first major con is the price. Lets not even mentiont he laptop cause most of use have access to either a laptop or a desktop and this ised would work for either one. But the cost of the projector can really hit your pocket. I have seen them for around 500.00 on e-bay but I really dont know which ones are any good.
A VERY MAJOR PRO is that it takes up absolutely no table top space. You can put all your stuff all over the place and only have to move it when the map starts to impeed.
Another pro is that the projector adds reading light to the table, thats always a plus when playing in a basement. And not to mention it looks reall cool!!!!!
Just putting my 2 cents in.. hope it helps!