Airplanes of the future may not look like George Jetson or Star Trek aircraft, but they'll be powered by anything from vegetable oil to algae.

Solar, biofuels, energy efficiency, wind, water  – not to mention  upstart stocks -- can be bewildering even for disciplined investors. That’s why a recent spate of green or clean tech exchange-traded funds  may be a welcome addition.

What started as a fringe movement of environmental activists and hippie entrepreneurs more than thee decades ago is becoming mainstream for companies, investors and consumers.

CEO Mike Splinter made a strategic decision to enter the solar business, a move that has already meant more than a billion dollars in investment.  And, yes, it is paying off.

Twenty years ago at the Port Authority of New York and New Jersey, Larry Filler came up with a plan to entice companies and workers into using more mass transit. Today , that qualifies Filler as something of a green trailblazer.

Rep. Paul G. Rogers helped win passage of the Clean Air Act Extension of 1970, one of the nation's most important pieces of legislation and a major  environmental milestone.

Danish political scientist and popular author Bjorn Lomborg is all for doing something about climate change but he is skeptical about some of the efforts, which is why he wants to bring the debate back down to earth.

CEO Carl Bass says buildings can set a good example for the green movement and his firm's software is making sustainable design make sense.

Water -- often overlooked in the green debate -- is a key part of the company's 2015 sustainability goals and a promising profit center in emerging markets.

Automakers are all for sustainability, but they need regulations and policies to make green vehicles popular enough to ensure profitability, says Booz Allen Hamilton's William Jackson.

The founder of the Starwood hotel empire is launching a chain of environmentally friendly, luxury hotels and condominiums in 15 cities. "We're going to try something and see if it works," says Sternlicht.

Former EPA boss turned business consultant  Christine Todd Whitman says we need national policies on energy and climate change and the lack of them is frustrating business, which wants "to do the right thing."

Oil expert Daniel Yergin says progress is being made in meeting our energy needs, but "innovation takes time to develop and unfold", while more emphasis needs to be put on energy efficiency.

From mutual funds that use shareholder advocacy to influence corporate behavior to exchange traded funds that focus on clean energy, it’s easier than ever for average investors to “go green” -- without sacrificing returns.