Looking over Juro's list of casts made me start thinking about the best way to classify casts. It seems to me that the basic differentiator should be the way you load the rod. That would leave us with five major categories of cast (that I can think of, at least):
1. Casts loaded by tossing the line straight backwards (e.g., overhead cast).
2. Casts loaded by tossing a looped line backwards (e.g., traditional spey cast)
3. Casts loaded by driving the rod forward against the surface tension of the line in the water (I think this is how skagit style spey casts work from descriptions I've read, but I must admit I don't really understand skagit casting)
4. Casts loaded by driving the rod forward against the dead weight of the line (e.g., roll cast)
5. Casts loaded by pulling on the line with the free hand (e.g., bow cast)
Within each of these major categories, you can vary the cast in the following ways:
A. Moving the rod on the forward cast to alter the forward trajectory of the line (e.g., wiggle cast or curve cast)
B. Making motions to reposition the line prior to loading the rod (e.g., snake roll, double spey)
C. Using hauls to energize the line
D. Altering the plane of the cast (e.g., moving from overhead to sidearm)
E. Some combination of A through D
There are also technique differences . . . such as using a bigger or smaller arm motion or using more or less of the lower hand in a two-handed cast. I don't know if these technique differences truly change the cast or simply alter the way a particular cast is executed to provide the right amount of power or control for the particular casting situation.
Anyway . . . just an idea to restart an interesting discussion about casting types . . .