Here are two sources, the first of which is the more substantive. The problem is even hard to approximate, but algorithms are available that achieve about $2\frac{1}{2} \times$ the optimal packing.
(1) Miyazawa, Flavio Keidi, and Yoshiko Wakabayashi. "Three-dimensional packings with rotations." Computers & Operations Research. 36.10 (2009): 2801-2815. (PDF download.)
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(2) E. Dube, L.R. Kanavathy. "Optimizing three-dimensional bin packing through simulation." Proc. Modeling, Simulation, Optimization. 2006. (PDF download.)
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