Update
I thought i’d throw together a little demo of marching cubes (seems like there’s been a lot of that lately 
).
My laptop isn’t very good but here’s a video anyway.
[video]http://youtu.be/SBysKUD5hYs[/video]
And an image as well.
Here is a link to the jME3 project/code if you want to run it or see how it works:
https://dl.dropboxusercontent.com/u/41648603/BasicGameGSOC.zip
I tried to keep it pretty simple.
For a much nicer demo see pspeed’s stuff:
http://hub.jmonkeyengine.org/forum/topic/marching-cubes-triplanar-mapping-multires-textures-and-lemur/
References:
http://paulbourke.net/geometry/polygonise/
http://http.developer.nvidia.com/GPUGems3/gpugems3_ch01.html