Ok, you've probably seen some images or straight up google style maps from a server or single player map. These are actually very easy to make! The only requirement is a little patience and testing.
First of all, you will need one of the following programs:
I will recommend Minetographer, an interface for the very powerful command line tectonicus. Here is a sample map generated by Minetographer
However, I will try to explain why I wont give an outright "use this one" ..! Not every program works under every OS, map type, size on disk, size by x/z co-ordinates. I used to use Minecraft Overviewer, but out of the blue it suddenly couldn't render my whole map, and would crash if I tried. Another died after somebody ran in one direction for a long while. Some of you may be on a mac..etc.
The best option is to grab what looks best initially, if it works on your map, fabulous, if not try another!
My initial map render took 14hours (300mb disk size) and weighed in at just under 1.5GB! However due to caching, the next render took only 20mins, redoing only what had changed. Hopefully this helps/inspires others to explore the possibilities. At the risk of flooding my host, http://www.wartywarlock.com/MCMap/ is our (slightly outdated) render.