While inside a ruby file, invoke the shortcut (supplied as Ctrl-S), and the corresponding spec will be open. The assumptions are:

• Your specs live in spec/ or fast_spec/
• Your pwd (current dir) is the project root
• You use the same dir structure in your code and specs so that code living at lib/foo/bar.rb has a spec at spec/lib/foo/bar_spec.rb

For more information, please see doc/spec-finder.txt. There are included functions for opening the spec in the current window, and in a split, as well as just getting its full path.

UPDATE: This plugin is now part of https://github.com/skwp/vim-ruby-conque