I second a vote for MyTopo.com. I ordered a map there last Thursday afternnon and it arrived at my door on Monday.
The deal that they offer is you actually choose the size, scale and border of your map. It comes on waterproof paper printed with waterproof ink. You can also specify if you want it grid marked for UTM, MGRS or Lat/Long.

I am old school and prefer the 1:50,000 DMA military maps, 15 minutes of lat/long with MGRS/UTM grid already printed. I do not know of a source although I am told you can order them special through the USGS.

When I ordered a special map from MyTopo.com, I specified MGRS grid and 1:25,000 scale. That way my military grid romer fits perfectly and the grid lines are already pre-printed. The map is 24x36 and takes in a lot more area than any single 1:24,000 USGS 7.5 scale map.

Hope that helps. I am going to look into the Army Corp of Engineers as a possible source of DMA maps! Cheers.