Soma Cube - Plain

This is Piet Hein's Soma cube puzzle. If you want to print one, Soma Cube, take 2 fits together better. 

If you want to play with the exact geometry of the pieces, however — maybe make papercraft nets or some such — this model is the one you're looking for. The OpenSCAD model uses only integer coordinates, and has been verified to produce valid geometry for all pieces.