The German amateur satellite organization, AMSAT-DL, has proposed sending an amateur radio satellite to Mars!

As envisioned, the satellite would be a "mother ship" for launching smaller probes that would transmit back information about the Martian atmosphere and surface,as well as a repeater that would beam that information back to earth.

For more information, see the AMSAT-DL website at http://www.amsat-dl.org/p5a/p5a-to-mars.pdf