I can also recommend two other similar video and lesson plan sites, LessonStream and Allatc (the latter particularly for more advanced learners) but what I particularly like about FilmEnglish is the choice of the clips: they so intrinsically interesting, as the materials for lessons really always ought to be.
And a couple more video sites: if you must turn everything, including YouTube material into grammar exercises, then Movie Segments to Assess Grammar Goals might be your thing, as might ESL Video, for creating your own exercises.
YouTube (not to mention other sites like Vimeo and Videojug) offers language teachers an amazing variety of materials but rather than immediately thinking "How can I turn this clip into an exercise?", think "How can I turn this into a lesson?" — particularly if it involves doing something more creative with YouTube.
The key question to getting the most from YouTube is probably to consider how active or passive the learners are going to be. If the clip gets them merely to check true/false boxes, they're passive; if it gets them to talk, then they're active.