I am in love with California Polytechnic’s CubeSat program. For $80,000, you too can have a very small satellite in low-earth orbit.
My CubeSat would be a time-capsule — it would have a tiny hard drive and would listen for new upload transmissions throughout its life. Then, when given a special command, it would engage its tiny air-thrusters and travel off into space. (You’re probably thinking “It wouldn’t be able to escape Earth’s gravity!” but come on — an iPod with a jetpack? It most certainly would.)
Any other CubeSat ideas out there?