You can send your name/callsign all the way to Pluto free of charge.
The New Horizons mission is due to launch January 11th 2006 to perform reconnaissance of Pluto-Charon and the Kuiper Belt.
All the names entered on the website below will be recorded on a CD which will be mounted on the spacecraft before it begins it's historic journey to Pluto and beyond.
Dial Up:
http://pluto.jhuapl.edu/ecard/sendNa...ntent_low.html
Broadband:
http://pluto.jhuapl.edu/ecard/sendNa...d_content.html
To get your call sign included just enter it after your last name, eg
John Doe/M0JAD
When you've entered your name there is a very nice certificate available for you to print out.