Steinn reports that the NRC has made its recommendations for NASA’s Beyond Einstein program. The winners appear to be LISA, a gravity wave observatory, and JDEM, a competition of dark energy focussed satellites. Steinn has lots of links to the various projects. The executive summary of the report is availabe here (pdf).
I know next to nothing about these things, but from afar it always seemed like LISA was one of those neat ideas that was never actually going to happen. The basic idea is to put three satellites in orbit around the sun and bounce lasers around to measure gravitational waves. To keep things stable, as I understand it, the lasers would be inside the satellites, but not actually attached to them. Not cheap, but it could possibly open up an entirely new spectrum with which to do astronomy. But, as I said, I know nothing of the politics or technical details, so hopefully some astronomer/astrophysicist can write something up.
Update: Sean weighs in.