Thanks to

Ben "poopinmymouth" Mathis
for the original concept

IC.GeoEdgeLoop refits one or multiple closed edge loops to regular polygons. It works on Editable Poly Objects and Edit Poly Modifiers.

On single edge loop selection two algorithms are available: Refit by Vertex and Average. On multiple edge loop selection only Average is available. The edge loop is flattened on the average plane.

Select one or more closed edge loops, run the script, follow on screen instructions. Right click aborts the command.
Autodesk 3ds Max 9+
Additional requirement for 3ds Max release 9 only
AVGuard MAXScript Extension Package 9.0.0 by Larry Minton
Download — version 0.4 — 2009.10.27 — 8.40 KBytes
Discussion thread on Polycount forum