Custom C# script in Grasshopper for Rhino. Implements the Chebyshev Net algorithm to generate a quad mesh which approximates the source surface whilst ensuring that all edges in the mesh are of equal length.
A similar approach was apparently applied in the design of the Savill Gardens gridshell (http://en.wikipedia.org/wiki/Savill_Building).
Here is a fantastic paper on the subject: http://www.graphicon.ru/2002/pdf/Popov_En_Re.pdf
Apologies for the dodgy screencasting skills!