A couple of upcoming missions have announced that the public can submit their names, which will then be attached to the spacecraft that is launched into space. I've done this with a couple previous space missions, and it's a cute thing, you can even get a certificate :-)
The two missions that I just became aware of that are doing this are:
Lunar Reconnaissance Orbiter - whose purpose is to "to [find] safe landing sites, locate potential resources, characterize the radiation environment, and demonstrate new technology." Send your name (and those of your family and friends) to the moon!
Kepler Mission - "specifically designed to survey our region of the Milky Way galaxy to detect and characterize hundreds of Earth-size and smaller planets in or near the habitable zone." Submit your name (and a brief message if you want) to be carried along on the spacecraft that may be the first to detect a possibly habitable extra-solar planet.