Brain Pop rocks! Be aware it is geared to elementary level learners. I like it because it could be used as a review or to reinforce previous lessons. I personally think I would use it as an introductory or culminating lesson.
Since it moves mind numbingly slow, it is great for new ELL’s, while at the same time, it will capture the student’s attention because the graphics are appealing. Also, there is a lot of repetition and visual reinforcements, which is a good thing. Overall, I feel that BrainPOP is a great free resource that should be part of every ESL teacher’s tool kit.