"Dan Meyer teaches high school math outside of Santa Cruz, CA, and explores the intersection of math instruction, multimedia, and inquiry-based learning."
Very neat website that converts files for you FREE. Upload a file to the server and tell it the format you want it converted to. In a very short time, you get an email and a link for your converted file
I've used this, too, and it's excellent. Very useful for saving Youtube videos that you may want to use in the future or integrate into Powerpoints, etc. I have found, though, that wait times for the converted file vary from 10 minutes to about 12 hours, so don't rely on it for next block's presentation.