NASA is currently running a programme till the 27th of june 2008 where you get to enter your name at their website
http://www.nasa.gov/lro. and it will be entered into a database which will be saved to a microchip.
the microchip will be attached to a NASA space craft called the Lunar Reconnaissance Orbiter which be launched later this year to the moon.
all names entered before that date will be carried to the moon and that's how it works.
for more information check out their website at
http://www.nasa.gov/lro.
i have already entered my name twice. so you should also enter yours.
after entering your name you will be issued a certificate that you can print out and show to people.