This seems like a fun site! It’s called Writing Exercises and has a whole grouping of different links. Prompts and games and all sorts of things.
I’ve looked at a couple of different links—the Random First Line and Random Dialogue along with the Anagram Game. Although the game doesn’t really have any directions, it didn’t take me long to figure out how to play (for the most part).
In addition to all the links, the site has an Android app which you can download (for free even!) but unfortunately not an iTunes compatible app. And even an ESL page.