Getting started with the Dropbox Ruby SDK:
1.  Install json and oauth ruby gems with:
    gem install json oauth
2.  Edit cli_example.rb to to include your APP_KEY and APP_SECRET
3.  Try running the example app: 'ruby clie_example.rb'.
4.  See dropbox_controller.rb for an example Ruby on Rails controller.  It needs an APP_KEY and APP_SECRET set too.
5.  Check out the dropbox website for reference and help! http://dropbox.com/developers_beta