Energy independence is free
This TED talk by Amory Lovins gives you a fast-paced overview on how investments in alternative energy and US energy independence provides such economic benefits that it becomes free (as well as our best form of homeland defense). Although this talk was recorded in 2005, I think that it is even more true today (and oil is even more expensive).
I think that this path is one of the most important things for a new president to pursue. The US would lower its dependence on foreign oil, would develop innovative products that we can manufacture here and export to the world, and would have positive environmental impacts against global warming.
I think that this is worthy of a 'space race' level of investment, or at least a 'DARPA/Internet' level. I don't want the government to own it, but I want to government to sponsor the basic research in our universities, fostering an awareness of this in our young people and providing a starting point for a host of new energy innovations and businesses.