You could try trolling the dunjinni forums, (
http://dundjinni.com/forums/) they have some really impressive maps up there, some of which might be right for what you want. If you're lucky, they've already broken the larger map into 1 page elements. I save those to my computer, open them up in any program that lets you have a ruler to check the 1" grid really is 1" (even Word would work) and do any resizing necessary. Then, I print them out on 110lb "cardstock" paper and cut away any margin. Depending on, I may even glue the maps to foamcore or you could use matboard (right now's a perfect time to get free foamcore- it's the end of the school year and teachers like me are tossing out old student projects which are often mounted on these sorts of material). Alternately, you could laminate the map which would help with the stiffness AND then you could write on it for spell effects, etc. A varient of that would be to get a large piece of plastic that you could lay over all your map tiles, which may be cheaper in the long run.
Have you ever considered going 3D to have a scene like
or
I stumbled across WorldWorks Games' website (
http://www.worldworksgames.com/store/) when I was looking for some battlemats. They sell for outrageously low prices ($15 is the highest I've seen!) sets of pdf files that allow you to print out cardstock terrain so you can build castles, villages, dungeons, caves, pretty much anything you want. They've also got a ton of modern, sci-fi and other themed sets. If you want one particular building or four of them, you just print out as much as you want. You cut it out, glue it, and you're done. If you want to get fancy, you can use a black marker to "edge" or cover up any white cut edges that might show up. I built a model of Vraath Keep from the module "Red Hand of Doom" over the course of two or three weeks. The nice thing is that I can now use most of the buildings from that model to create other locales, etc. I'm building up a supply of generic buildings as well as module specific so that I can slap together quickly pretty much any scene I want eventually. If you want to take a look at the keep I built (with little experience), you can scroll down through my recap thread at
http://boards1.wizards.com/showthread.php?t=793120 and see some pictures. Be aware the green building is my crappy attempt to make my own buildings before I found the worldworks stuff.