Build a Welder From a Salvaged Microwave

http://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/
I got this link off the Survival Blog.

Here also is one on how to make one from 2 car batteries: http://www.ehow.com/how_6040123_make-welder-two-12_volt-batteries.html

Always wear dark eye protection and thick gloves when welding.  A leather apron might be a good idea too.  The apron you could make out of an old leather skirt from the thrift store.