Userscripts.org

Doesn't work on Chrome.
Such a shame.

I'd really love this for Chrome too, but I understand not wanting to spend time on it if you don't use it yourself. It's weird how Netflix and Rottentomatoes partnered so that you can add movies to your queue on RT but there's no option to have RT scores populated next to movies in Netflix.

Until a better option comes along, I found a bookmarklet on Hackingnetflix.com that automatically searches a movie on RT when you're on the Netflix page:

javascript:location.href='http://www.rottentomatoes.com/search/movie.php? searchby=movies&search='+encodeURIComponent(document.title.substring(9,document.title.length));