Why: Mainstream use of electric cars could benefit the environment, especially where power is produced relatively cleanly.
Key innovation: Nissan's new electric car, the Leaf, has a reasonably modest sticker price of $32,000.
Why: Hybrid cars can significantly reduce gasoline consumption by using an electric motor alongside a gasoline engine.
Key innovation: A market leader with its Prius model, it is developing battery technologies that are helping to make these cars less expensive and more energy-efficient.
Why: Budget cuts will force NASA to rely on private companies for supply missions and other tasks.
Key innovation: Introduced a low-cost production method for everything from rocket engines to astronaut capsules.