In your movies folder (where Front Row pulls from) make a folder with the movie title.
Go to where you store your RipIt files and select the movie you made a folder for. If you have the .dvdmedia extension on the movie, right click to 'show package contents'.
Take out the Video_ts folder and put it in the folder you made in your movies folder.
If you're using an external hard drive, make symbolic links from your account's Movie folder to point to the actual movie locations.