Bryan Ewert had a wonderful collection of MEL bits and pieces at http://ewertb.soundlinker.com/maya.htm and a specific introduction to MEL at http://ewertb.soundlinker.com/mel/mel.095.htm

You won't really learn coding style and patterns from this, but its great for down-to-earth, learn-by-doing-it stuff. And taking a closer look at the scripts you use will help you a lot learning micro problem solving tricks.

But beware, a large percent of the scripts from HighEnd3D has awful coding style. Just the fact that a script works does not mean you should take it as being carved in stone. :)