These rhombic dodecahedra are unconnected, yet inseparable. They have been specifically sized for the Dual Replicator, in such a way that both extruders can be used at once (using JoeyC's script), to print different color interlocking polyhedra.
This thing turns out to be pretty fun to play with; it makes a decent rattle and I enjoy the game of hanging onto one end and trying to swing it to make all six modules stack upright.
If you're using a Dual Replicator (or similar), skein up halfchain3.stl and then use JoeyC's script so that all 6 are printed. If you'd rather print with just one extruder, I'd recommend chain6.stl, or you can open the SCAD file and output any number of modules at any scale.
This prints beautifully without support, and due to the large bottom face, it sticks to the platform quite well. I had some trouble with Skeinforge, so if you run into problems, I'd recommend using Slic3r (0.9.2 works great on the Replicator).