There are derivative markets where you could purchase an option to sell bitcoin at a set price in the future. If the price falls below your target by then, buy up cheaper Bitcoins and sell them at profit.

https://bitfinex.com allows short sales on bitcoin.

Thinking the same thing. It'll be interesting to see somebody going out sorosing the BTC "economy".

If you really want to - Borrow $x bit coins - sell $x bit coins - wait for price to drop - buy back $x bit coins - return $x bit coins to lender.

Now the speculators are in........

Good luck. I hope it goes better for you than the people planning to do it 3 weeks ago. Or 3 months ago. Or a year ago.