Files

file uploading:
http://www.tutorialspoint.com/ruby-on-rails/rails-file-uploading.htm
in pdf
http://railscasts.com/episodes/134-paperclip?autoplay=true
https://github.com/thoughtbot/paperclip

Encripting files:
http://onehub.com/blog/posts/encrypting-your-files-with-rails-part-i-2/
http://onehub.com/blog/posts/encrypting-your-files-with-rails-part-ii/

Hirb, to see nicer tables in irb (rails c)
You have to add gem 'hirb' in the gemfile
https://github.com/cldwalker/hirb