Solar City is one of several companies doing a leasing program for rooftop solar, that's hardly innovation. Worse, there doing rooftop solar which is far worse than grid connected solar which is worse than wind. Still, there likely making money and it sounds good.
Tesla is also something of a tossup, right now there cars are terrible for the environment, but that might change long term.
Nest is something of an odd duck. There worse than several other thermostats when it comes to saving energy, but adoption has been really poor in this area so it's probably a small net win.
I don't really see the benefit to Uber as they increase traffic relative to hailing a cab. There might be a net benefit to surge pricing though.
In the end Startups tend to be poor places to do real environmental impact simply because most issues are really large scale. Bumping a coal power plants efficiency by 1/10 a percent has a massive impact which is hard to reach on the small scale.