Letterboxd Movie Assistant (dlicmihnogpoemhcegbnhbmncbkoidjo): Shows a page action for imdb/rotten tomatoes film pages to go to the letterboxd equivalant... Read More > or Download Now >
Adds an icon in the address bar that comes up on Imdb and Rotten Tomatoes film pages. By pressing this icon a new tab will open that goes to the letterboxd film page.
*Note: This extension is not made by the letterboxd team but someone who is a big fan of their site!
Update 4/17/15 - Fixed the bug with Rotten Tomatoes so its now working again from there!