http://www.hd-bb.org/ has high quality rips, MKV often from Blueray.
I get the "m-HD" mostly.
Otherwise use a search page like
http://www.filestube.com/http://rapidqueen.com/Avoid the "full download" bait-and-switch links though.
For a specific movie, seach for its IMDB number. Even a normal Google seach for that + "Rapidshare" often finds it in some obscure blog.