A lot of English learners wonder why English words are often spelled so differently from how they are pronounced. One of the main reasons is that English underwent a transformation called the Great Vowel Shift, which preserved Middle English spellings even as the pronunciation of the words changed.
Sorry for tooting my own horn, but the students in the class really enjoyed it, and now that my husband has finished making the video I thought I'd share it here. :)
Part 1: http://youtu.be/JdwzVxbqsB0
Part 2: Should be uploaded this weekend!