ruby_run.vim is a simple plugin for executing a ruby buffer or a selected block of ruby code.
Default mapping are:
noremap <silent> <C-E> :call RubyRun()<CR>
vnoremap <silent> <C-E> :call RubyRangeRun()<CR>
If you don't have a preferred installation method, I recommend installing pathogen.vim, and then simply copy and paste:
cd ~/.vim/bundle
git clone git://github.com/stjernstrom/vim-ruby-run.git