This list contains suggested gems for specific problems. If you find any specific gem, which should be treated as a "standard", please add it below.
- httparty - easy way to wrap http responses
- roar - very flexible way to create JSON representation of resources
- roar-rails - include roar into rails
- devise - auth & more
- devise-async - sending devise emails in background
- sidekiq - threaded background queue
- whenever - scheduler
- schema_plus - support for foreign keys, database defined validations and associations for postgresql
- better_errors - replace standard rails error page with more useful version
- miniprofiler - profiler for database queries and time spent loading parts of page (go to discussion)
- pry-rails -
rails consolereplacement
- guard-livereload
- letter_opener - see sent emails in browser
- rack-livereload - autoreload assets & views
- coffee-rails-source-maps — support for CoffeeScript source maps
- active_link_to - easy way to handle active links
- select2-rails - fancy select and autocomplete
- simple_form - DSL for generating forms
- localized_language_select - select tag for language
- country_select - select tag for country
- activeadmin - admin panel for free
- auto_strip_attributes - automatically strip whitespaces
- carrierwave - file uploads
- decent_exposure - helper for creating declarative interfaces in controllers
- friendly_id - slug generation
- rails_config - miscallanous settings for different stages
- capybara - webrat replacement
- database_cleaner - ensure a clean state during tests
- factory_girl - fixtures replacement
- factory_girl_rails - factory girl integration for rails
- rspec - testing framework
- rspec-rails - rspec integration for rails