Based on good work found at http://goo.gl/bKjJe
If you have Nginx running, you can run Yard as a rack app to serve docs for locally installed Gem.
- Create a directory to host Rack app. Install yard gem
 
mkdir -p ~/Dropbox/yard/public
gem install yard- Add config.ru as 
~/Dropbox/yard/config.ru - Add Gemfile as 
~/Dropbox/yard/Gemfile - Run 
cd ~/Dropbox/yard; bundle install - In nginx config, add gems.doc virtualhost
 - Add a localhost alias 
gems.docto/etc/hostsfile. - Restart nginx and access http://gems.doc:8010 to see docs.
 - You'll need to re-start nginx everytime you add new gems to your Ruby installation.