Hi, all. I am doing GM after school (and did so this summer) so thought I'd respond a bit after skimming the thread.
First, Duke's energy and environment concentration is brand-spanking-new. Minted just a bit ago. It's exciting, though, since Blair is so behind it (Blair Sheppard, I mean, the dean.) We also have an increasing number of students doing joint degrees with the Nic School, so they'll also get a master's in environmental management (a MEMMBA!). Most, if not all of them are doing the energy track at the Nic School, and want to do energy work. I've got a number of friends who did energy internships this summer: one did a wind financing gig, another was in solar, a few at Chevron, Exxon-Mobil, and I think somewhere else....but don't remember where.
And I'd add finance companies to your GM list: Citi, B of A, M&T, BB&T, D&B, Thompson, AmEx, and others all recruit at Duke. (That's what I do!)
I've also seen plenty of roles in tech-y companies: Sprint, Apple, Microsoft, Intel.
I will point out that they don't all do rotations - sometimes you come into a company in a certain role, and then you get to move around as you get promoted.
Hope this is helpful.