Heheh, I made this very thing 5 years ago. It was working and functional for our MUD, although still missing features to make it really awesome.
It's funny I had forgotten completely about it, but it's a neat little program. You might want to check it out. http://tempusmud.com/~jwatson/jCarto/
There is a tutorial up there, as well as a working compiled distro (although there is no .jar or launcher, use the sh script what comes with it to start it under cygwin/linux, or just look in the script to see the options and main class).
Heck the thing even has a nice little A* alg to draw the links between rooms. The Exit edit panel appears nonresposive for some reason but what do you expect from a program that's sat idle for 5 years. Oh and the source code is available too.