For what they're worth, I've posted some heavily commented MathProg (GMPL) examples for a short course that I've been teaching over the last month. They're available on the site:
http://estm60203.blogspot.com/. You'll find source attributions in cases where I've used problem data from others. Others were developed from scratch.
Perhaps those new to GMPL will find these useful. I'd appreciate any and all feedback or advice.