Erotic art and photography is also something that is very sought out by collectors. The same goes for many photographers in the 40s and 50s. Now that their works of art have been discovered, they are being sought after by many collectors.
The bottom line of all of this is pretty much if you have any vintage erotic books, posters, works of art or movies, holding on to them is not such a bad idea. You never know what they might be worth.