I'm not very knowledgeable about shaders and/or the programmable graphics pipeline generally, but I'm looking to do something very basic. If I have a model that is almost entirely rectilinear -- like a lego block structure or something -- what's easiest way to render it cartoonishly, meaning flat color on the faces of the rectilinear model and the edges outlined in black. I know how to do this with textures but I figure this must be really easy to do with shaders. Can someone point me to a tutorial or some code somewhere?

This should answer your question

The thing is I'm not really looking for that sort of cel shader, it's just the closest thing to what I want that I can easily name. Basically what I want is a shader that will generate a solid wireframe render of the model where the edges of the model that are between two parallel faces are not shown, just the ones between faces that are at n degree angles or greater, where n is a constant. This has got to be really easy to do, and I thought maybe there was some tutorial somewhere that shows how to generate a solid wireframe like this as a sort of basic example before building on it to do something more complicated, but I couldn't such a basic example.

Then find a cel shader, and modify it to your needs.