http://www.howstuffworks.com now contains info about turbochargers, it had a little section in its info on superchargers but it was quite insufficient.
http://auto.howstuffworks.com/turbo.htm
I found the information good to get a basic understanding of how they work, it doesn't explain that a properly sized turbo shouldn't undergo much lag and that sequential turbos are complicated and basically obsolete because of ball bearings. people who are new to turbos should check this out.