For awhile you could submit your name and NASA would etch it onto a microchip that they then installed on the Curiosity, to take to Mars.

http://marsparticipate.jpl.nasa.gov/msl/participate/sendyourname/

"Thanks to all for submitting your names. You are on your way to Mars!
Your names are being prepared for etching on a microchip that the Curiosity rover will carry on its "back" (its "deck"."