These are the tutorial Cutebuns did, they are really good but you might have to go through quite a few pages of info
http://www.quiltingboard.com/t-35100-1.htm
http://www.quiltingboard.com/t-35685-1.htm
http://www.quiltingboard.com/t-36316-1.htm
http://www.quiltingboard.com/t-36954-1.htm
or you could get one of the books by Maxine Rosenthal and Joy Pelzmann.
I have One-block wonders Encore and it covers the basic OBW and some of the cubes.
The first book also covers OBW done in octagons and the 3rd book One-block wonders cubed has some of the basics and more of the 3D cubes.
There are a lot of people here to ask for help if you get stuck at any stage.
Hope this helps.