sheet metal resource material

Currently looking for sheet metal resource material (ie reference guide, principles, etc.) - preferably online. Does anyone has any good links to share?

thanks!

google.com … . .


Mechanical Engineering Tools, Manufacturing Tools,Design and Manufacturing Calculators Design Reference
http://www.industrialpress.com/en/Item.asp?BookID=181
http://metals.about.com/od/sheetmetal/

hard to find all of this in one place.