Horror movies are one of the most popular depictions of Japanese spirit lore. In these movies, spirits are portrayed as the things of nightmares, as you can see to the right with a movie depicting unforeseen horrors in the Aokigahara (suicide) forest. This film takes the lore from a dense forest that is known for its high rates of suicide and creates a chilling tale around "true" events.
Horror movies use spirits in other films such as The Ring, The Grudge (also depicted to the right here), and Dark Water, just to name a few.

These themes of vengeful Japanese spirits who had lived through horrors or who want to make those still living suffer is how Yōkai are portrayed. While this can create a ominous feeling about the Yōkai, it does assist in spreading the essence of the lore.

Anime and Manga are another extremely popular form of telling of various types of Yōkai folklore.
Yōkai are not only spirits - they are defined to also encompass most other supernatural beings (excluding giants).  The word, from Kanji,  translates to mean "bewitching; attractive; calamity"; and "spectre; apparition; mystery; suspicious". (Wiki)

To the right is a very popular series that is an example of various parts of the Yōkai's supernatural world. Inuyasha (the dog/demon/man) is of supernatural genetics and Kagome is a generations down reincarnation of a warrior priestess from the feudal times. And together they work to put a magical sphere back together and battle many different types of Yōkai in the process. This is of course just one of many examples of folklore being used and adapted to appeal to a younger generation as well as used to reach people outside of their country.