If somebody is interested in I hacked up some test to use blender to build some lego models. The code is mainly proto so …
Simple screenshot from http://odin.wipsl.com/~mikasa/static/LegoThird.png
To start up the addon. Change the directory variable at the LegoBuilder.py to point to the directory you uncompressed the tgz. Then ALT-P or Run Script to run the script. Then in the View3D there should be Lego Colors and Lego Bricks Toolbox. Open the Lego Bricks and expand one category (e.g. bricks) by pressing the small triange icon. Then press the brick name with left mouse and it should be appended to the view3d.
One important thingie: Some blender object must be selected before new bricks can be added with mouse. This issue will be removed once there is PythonTab added (if there ever be one).
AddOn + ldraw library + bricklink XML files from : http://odin.wipsl.com/~mikasa/static/blego.tgz
Not sure if it is really working in other machines than mine. Anyways there is some example core for ldraw importer e.g. if the script wont start up