If you change the "all" at the search box at the top of the page, select "advanced search," you'll see a link to
Browse Videos . You'll get the list alphabetically, and you can also jump to a letter.
There is also a link to
Search Videos.
You can also choose
Advanced Title Search and choose what to include/exclude and under "Instant watch options," you can check the box for "Free on IMDb" and get a list based on your search parameters. You can even, if looking for something you haven't seen, exclude those you've seen (as in, those you've rated on IMDb-as that's the only way the system knows you've seen them). Checking that, though, it will include any video, not just full movie for free. So if it has a featurette, etc., it'll include it even though not the full movie.