Space Solar power
Space Solar Power (SSP) gathers energy from sunlight in space and transmits it wirelessly to Earth. Space solar power can solve our energy and greenhouse gas emissions problems. Not just help, not just take a step in the right direction, but solve. Space solar power can provide large quantities of energy to each and every person on Earth with very little environmental impact. For details see http://www.nss.org/settlement/ssp/index.htm -- this includes full text of most SSP studies over the years.
Many believe SSP is too expensive for serious consideration, but two companies, Solaren and the Space Energy Group, have contracts to deliver SSP and there is some reason to believe SSP is not much more expensive than nuclear power today, and some serious R&D could drive that cost down. Note that the key to successful SSP, lower launch costs, is a major component in the administration's new space policy. Also note that DOE has budgeted $400 million for fusion research, with little chance of economic power anytime soon, and 0 for SSP. For details on the comparison with nuclear costs, see http://alspolitics.blogspot.com/2009/11/is-ssp-competitive-with-nuclear.html