Those DARPA guys (yes the ones that started this internet thing) have now come out with what they call as "a "Mathematical Challenge", that has the mighty goal of "dramatically revolutionizing mathematics and thereby strengthening DoD's scientific and technological capabilities."
The challenges are in fact 23 questions that if answered, would offer a high potential for major mathematical breakthroughs, DARPA said. So if you have ever wanted to settle the Riemann Hypothesis, which I won't begin to describe but it is one of the great unanswered questions in math history, experts say. Or perhaps you've always had a theory about Dark Energy, which in a nutshell holds that the universe is ever-expanding, this may be your calling.
Well, the last date for cracking these problems is over (I wonder why they have a last date for such mighty difficult problems; can they not be solved after another month, or do thse problems come with an expiry date?). But check out the list at : http://www.networkworld.com/community/node/33361