jazz_hands
jazz_hands is an opinionated set of console-related gems and a bit of glue. Including Pry, an awesome REPL, & some of it's friends. Pry is is a powerful alternative to the standard IRB shell for Ruby. It features syntax highlighting, a flexible plugin architecture, runtime invocation and source and documentation browsing. It also includes awesome_print.
https://github.com/nixme/jazz_hands
https://github.com/michaeldv/awesome_print
xray-rails
Xray is the missing link between the browser and your app code. Press cmd+shift+x (Mac) or ctrl+shift+x to reveal an overlay of the files that rendered your UI, and click anything to open the file in your editor.
https://github.com/brentd/xray-rails
better_errors
Better Errors replaces the standard Rails error page with a much better and more useful error page. It is also usable outside of Rails in any Rack app as Rack middleware. Add binding_of_caller for REPL fun in the browser!
https://github.com/charliesome/better_errors
mini-profiler
Middleware that displays speed badge for every html page.
https://github.com/SamSaffron/MiniProfiler/tree/master/Ruby
guard and the guard dynasty
Guard is a command line tool to easily handle events on file system modifications
https://github.com/guard/guard
https://github.com/search?l=Ruby&langOverride=&q=guard&repo=&start_value=1&type=Repositories
https://github.com/guard/guard-livereload
devise
Flexible authentication solution for Rails with Warden.
http://blog.plataformatec.com.br/tag/devise/
https://github.com/plataformatec/devise
t
A command-line power tool for Twitter