If going for $1,000 isn’t exciting enough for you, consider this from Sean Gabb of The Libertarian Alliance in the UK:

If you have not done so yet, please consider for
yourself or for your students the Chris R. Tame Memorial
Prize. You need to supply me, on or before the 1st October
2007, an essay of around 2,000 words on the subject:
“Does Britain Need a Libertarian Party?”

Whoever writes the winning essay will get £1,000 (ONE
THOUSAND POUNDS STERLING). This competition is open to
everyone in the world except officers of the Libertarian
Alliance. Just because you may not be British does not
prevent you from offering us advice!

You can find the rules of the competition here:

http://www.libertarian.co.uk/conf07/prize07.htm