Cleaning up the trash in space.
Raising the Dead - Satellites that is: DARPA has selected a first spacecraft for its orbital recycling program. The idea makes a lot of sense, not only does it reduce dangerous space debris, but all objects in orbit have a very high intrinsic value based on the energy expended to put them there (it costs tens of thousands of dollars per kilogram to transport items into space).
Once fully realized, Darpa envisions the Phoenix program, which the agency wants to fully demonstrate by 2015, working something like this. First, a servicing satellite — complete with mechanical arms and other “unique tools” designed specifically for the program — would be launched into geosynchronous orbit (GEO). After that, the agency wants to launch an array of what they call “satlets” — wee, bare-bones satellites — to meet up with, and be stored by, the program’s primary satellite.
Aside from the direct benefits of making dated space hardware useable again, many aspects of working and manufacturing items in space demonstrated by the program will be of great benefit to future endeavors.