While talking to Zach I got inspired to model lego bricks in order to create custom bricks - the ones you always wanted but thought you never could get. Well now you can!
Of course it does not snap in place as nicely as original lego bricks but it should be good enough to create the custom lego piece you always wanted.
Because the Makerbot we are printing on is so incredible fast that the knobs used to stay molten so I also included a version that has hollow knobs.
To generate other sizes our under development and undocumented MetaCADEvaluator plugin is needed. This is part of the development version of CSGEvaluator for Art of Illusion: http://objects.reprap.org/wiki/Builders/Metalab/AoI_CSG_Evaluator