I've always used
www.terraserver-usa.com. You have to pay for maps, like if you want one laminated and what not,but I always print them out for free and it works just fine. Or if you want a large map, you can save the picture to your computer and enlarge it with a photo editor then print it out in sections and laminate it. Haven't been to that site in a while, but it used to be a good one for topos.