Vim-railsapi is a project mainly written in ..., it's free.
Vim plugin that searches http://railsapi.com/ for Rails API
This plugin allows you to browse railsapi.com from Vim. It will invoke Firefox on Linux/Windows from the command line or default browser on Mac OS, and open the query in a new tab.
Inspired by apidock.vim
<Leader>ra
- search word under cursor