There are quite a few options. In addition to PostRazor mentioned, you could also use print services. Gameprinter (username here) does printing and shipping as well as selling of some specific content maps that you might find useful. Unfortunately, I don't have the link to his site handy ATM.

Another option is to not print the maps at all and use a Virtual Table Top application. This is especially good if you have some form of external monitor such as a big screen TV or projector OR all players use computers during the gaming session. Redrobes actually writes one such application (Viewingdale, link in his signature) and there are many others on the market, both pay and a few free. Personally, I use Maptool(RPtools.net) along with a projector when playing with my face to face group. Another good thing about using VTT's is that you can play with people all over the world (or say an old friend who lives half way across the country). Different VTT's have different features as well as price, so you may want to spend some time looking at them (most of the commercial ones offer a short time beta for try out reasons. )