Get your Dropbox variables right in the provided script, save it as a .sh file in your ~/Library/Scripts folder, assign it to a shortcut in FastScripts, and you're a keyboard shortcut and a few seconds away from taking a screenshot and having it automatically uploaded to a public folder. Awesome, and doesn't rely on imgur like csexton's captured (http://github.com/csexton/captured), which I was also investigating.

Works perfectly with scriptaculous.