Animoto.com - is a great video maker that can be another great tool for teachers to use with their ESL students.
I really think that this could be a great extra project for students to expand their understanding of any subject. Through the use of pictures and text ESL student can really get a better understanding of nearly any topic they are studying. From history to pop-culture students can make videos that can help them practice what they are learning in class.
Depending on the topic given to the students the performance indicators would be how well they stay on topic. Also how well they link the pictures to the text meaning they provide. The task could be very specific, such as make a video of five national parks and describe the pictures you choice to represent each park using the vocabulary words of the week. To assess I could see how well they use the words. At the end of the project I could do a quick word matching quiz.
Example Video -