Quick question: Does any site offer the ability to short sell?

[Xtal]

would be a pretty cool feature to add 

[drakahn]

https://icbit.se/

[Xtal]

https://icbit.se/

Thanks! looking at it now.

[Stephen Gornick]

would be a pretty cool feature to add  

There are also options.  

You could buy a PUT, giving you the opportunity to sell your bitcoins at a higher price even after the price goes down as you suspect it will.
Or you could sell a CALL option, and you collect the premium now.  When the price goes down the CALL expires worthless and you profit.

 - http://en.bitcoin.it/wiki/MPEx

and some peoeple are offering options through Bitcoin-OTC.