This site has many quality photos and detailed descriptions of the process used to build both a five string fretted bass and a fretless six string bass.

This site includes a lot of information about the design, construction and related issues involved with building an electric basses. Includes illustrations, pictures and descriptions in the construction section.

A journal on the construction of a four string, fretless electric bass.

Mostly pictures describe the construction of this bass made of a unique design.