I'd like to know which
gedit plugins I could install to make programming for Ruby and Ruby on Rails easier?
sudo apt-add-repository ppa:ubuntu-on-rails/ppa sudo apt-get update sudo apt-get install gedit-gmate
and activate the plugins you want from options menu. It will activate sintax highlighting for erb files and many snippets for RoR developing.
Some more hints can be found here: http://rbjl.net/22-rubybuntu-4-make-gedit-better-than-any-ide. Some commands for the "external commands" plugin (e.g. "run in irb") can be found in this post: http://rbjl.net/23-gedit-external-tools-ruby-helpers-git-integration-and-more
I'll update the post with some newer plugins soon (e.g. the useful zoom plugin) and check if everythings is still working (e.g. rails-footnotes).