Thanks, Darkware, but I'm looking for a way to do this in MEL. I'll explain below.
Mark, thanks for the suggestion. AFAIK, that's the one of the simplest ways to get the shader from an object. But, as you said, that's only for shapes with a single shader. I am looking for way to do this at the face level for shapes with multiple shaders applied.
This is what I've found so far:
https://www.ewertb.com/maya/mel/mel_a43.html
Doesn't look too complex, just a bit convoluted. I'll dig into it some more tomorrow night when I have the brain power to do it.
For those of you who are curious (other than Mark 
), I'm writing a series of scripts to help me with my UV mapping process. My method of UV unwrapping is very similar to Craig Daughtry's (see his VIP tutorial) and is actually something I was doing in 3ds max long before I moved over to Maya. What I do is create several shaders with random colors and then visually plan out my UV shells by applying different shaders to face selections. Once I have all my faces assigned with shaders, I'll go through and planar project best fit on each of the "patches".
Here's what my mesh looks like when I'm assigning materials:
At the moment, I have a script that will automatically apply the planar projections and layout the resulting shells, but that script depends on specific shader names (I have another script that generates a user-defined number of shaders that are named correctly). I'd like to make the script a little more flexible by not relying on specific shader names. Basically, I want to generate an array of all shaders that are applied to a particular shape and then use that list of shaders to run my script.
Another thing I'd like to do is create a HUD element that displays the shader of the currently selected face. This is mostly to help me in my shell planning phase. It starts getting a bit crazy when I have 50+ shaders applied to my model, and I have to change shader assignments to just one face.
Anyhow, this is the moderately long answer for why I started this thread. Any help you guys can offer would be greatly appreciated.