Bloom Energy makes Solid Oxide Fuel Cells that are able to power an entire home, and fit in the palm of your hand. These fuel cells have been used by Google and eBay to provide part of the power used on their campuses. The company's CEO, KR Sridhar, originally created technology that was meant to produce oxygen so that people could live on Mars. When NASA scrapped that project, he reversed the technology so that it pulled in Oxygen instead of pushing it out.
The fuel cells use a substance similar to beach sand made into a ceramic wafer that is coated with a "secret recipe" of green and black inks. Oxygen is fed through one side, and fuel through the other to produce electricity. These fuel cells are different from the more standard hydrogen fuel cells because they can run on natural gas, bio gas, or even solar power. They also do not use the expensive metals like platinum that standard fuel cells use, but instead use a cheap metal alloy. Google has been using them to power a data center, and eBay uses them on their San Jose Campus to provide 15% of the power used there. eBay CEO John Donahoe said, "They have been very successful thus far. They have done what they said they were going to do."
If these can be produced on a large scale, and the price can be accessible to the general public (a big if, at this point), this could be a great energy saving solution.
See KR Sridhar's 60 Minutes interview from last year: