If you like the idea of tech contests–think ANSARI X PRIZE and DARPA Grand Challenge–and you also like space, then NASA wants you.

It needs ideas for the Centennial Challenges, prize contests with $20 million funding in 2005. Current ideas include: Mars and asteroid microspacecraft missions, lunar robotic landing, robotic triathalon, rover survivor, Antarctic rover traverse and extreme environment computer.

More here.
and here.