http://mycroft.mozdev.org/search-engines.html?category=31

...to search the IMCDB database directly with the little search box.

I looked for it several times in Firefox add-ons with no result, but found it here. (just click on imcdb and it will be added)
Thanks to "Steven"...

I was doing that since long time with keywords actually.
Make a bookmark to this url: http://www.imcdb.org/movies.php?title=%s
put "imcdb" in the keyword field of the bookmark properties.
then you can search a movie by typing in your address bar "imcdb" followed by the movie title.

Lots of type work. It's easier to just place the search box next to the address bar, and customize the search engines a little. (I think youtube wasn't default)

With this you can also select a film title (anywhere in a page) right click and "Search IMCDb for"... No typing, no copy and paste, just 2 clicks and you're there.