L-Girder construction is light, strong and versatile. It can be adapted to any layout design. Here are some web sites I’ve dug up on the subject.
http://rail.felgall.com/lg.htm
http://www.freewebs.com/aandbr/layoutconstruction.htm
http://www.ucwrr.com/construction.htm
http://benchwork.ryta.be/benchwokr.html