Links
Excellent tongs building tutorial
http://www.blksmth.com/tong_article.htm
Excellent blacksmithing resource & forum
http://www.iforgeiron.com
Excellent basic blacksmithing fundamentals
http://autonopedia.org/crafts_and_technology/Metal_work/Metalworking-The_Basics/6_Blacksmithing.html
Lots of How-To’s
http://www.lostcrafts.com/Blacksmith-Main.html
Useful Diagrams
Tongs, source: