How to find (and use) the codes
Netflix's hidden master list of content categories is huge -- it's organized into literally thousands of subgenres, and they get as specific as you could imagine, from Deep Sea Horror Movies, to Campy Crime Comedies, to Suspenseful Movies starring Michael Caine. To start exploring, hit either What's On Netflix or NetflixCodes.me to find lists of all the micro-genres and their corresponding codes. Once you've found a genre you're interested in, simply tack on the applicable numerical code to the end of this URL, and you'll see all the shows and movies currently available in that category: http://www.netflix.com/browse/genre/###
For example, if I wanted to watch a weird, funny movie, I'd plug in the code for Critically-acclaimed Quirky Comedies (1577), which gives me a lineup of available titles that fit the bill, including Frank, Amelie, Moonrise Kingdom, and Dope. Or, say I wanted to learn something while also crying. I'd drop in the code for Emotional Documentaries (1271), which would retrieve dozens of options, including Blackfish, Holy Hell, and How to Survive a Plague.