Saga's new OK-2 Do It Yourself Banjo kit offers a professional sounding instrument at a very moderate cost and gives you the thrill of accomplishment after creating your own custom banjo. All difficult work is already done for you and clearly illustrated instructions make it ever easier.
How (not?) to Make a Banjo
This website gives a step by step detailed instruction with pictures showing how to build a banjo.
DIY Life - Make a Banjo
DIY Life features a tutorial for building a tin banjo.
Build A Banjo
This site provides detailed instructions on how to build a banjo. Also provides templates and a list of part sources.