Folsom Labs, San Francisco, Full Time (www.folsomlabs.com)
Basically, if you are interested in science and/or energy, and want to do software engineering at a place that actually let's you leverage the math/physics you learned in college/grad school, we're probably as good a fit as you'll find.  We make powerful design tools for Solar PV systems, making them very easy to use by leveraging a pretty sophisticated simulation engine (so we handle the physics for the user).
We've already launched our product[1], have some great traction (including a federal grant), and we're still just a 2 man team, so there's a lot of opportunity.  Everyday we get to deal with a range of problems that few startups get to offer – we have a pretty modern web-stack [2] (that we actually need, not just to be trendy), but also get to solve interesting physics/optimization problems on a regular basis. It's a really unique place in both the solar industry, and as a software company.
– Paul
REDACTED_EMAIL
[1] <a href="http://www.greentechmedia.com/articles/read/better-faster-bankable-solar-pv-installation-designs-from-any-computer" >
[2] AngularJS, Python/Flask (API/Backend), Cython/C (Physics Simulation Engine)