What's the easiest way to work on a plain-ole Ruby gem, and then quickly turn around and run it in a Rails app?
I like to keep application logic out of Rails. Encourages code reuse across projects, and keeps my Rails app clean. It produces, however, an ugly workflow:
gem build ...
fury push ...
gem 'my_gem', :path => "~/my_gem"
You'll still have to restart the Rails server every time your code changes to reload it, but you won't have to go through the whole build-and-publish step for each revision. Be sure to update your gem reference to something production-worthy before pushing your code.