To generate google maps in ruby on rails is so easy and simple. I had recently generated a few maps in my projects by  YM4R/GM plugin.
There are few steps that you need to follow to generate simple gmap.
1. Install YM4R/GM plugin in your rails app.
ruby script/plugin install svn://rubyforge.org/var/svn/ym4r/Plugins/GM/trunk/ym4r_gm
2. Copy  the javascripts files from YM4R/GM plugin [...]