Since I'm just about to take delivery of two new steel lugged frames I thought a spot of reading would be good. Found some good resources
http://en.wikipedia.org/wiki/Lugged_steel_frame_construction
Why choose steel and lugs anyhow?
http://www.terrafermacycles.com/joinery/lugs/lugs.htm
Henry James produces many of the fine lugs
http://www.henryjames.com/productlug.html
Interesting read about a newbie frame builder having a go, includes a tutorial
http://www.littlefishbicycles.com/framebuilding.html