I recently discovered:

Matrix Structural Analysis, 2nd Edition, by McGuire, Gallagher, and Ziemian.

which is available for free download:

Description

The aims of the first edition of Matrix Structural Analysis were to place proper emphasis on the methods of matrix structural analysis used in practice and to lay the groundwork for more advanced subject matter. This extensively revised Second Edition accounts for changes in practice that have taken place in the intervening twenty years. It incorporates advances in the science and art of analysis that are suitable for application now, and will be of increasing importance in the years ahead. It is written to meet the needs of both the present and the coming generation of structural engineers.

The book includes a link to a free Matlab based frame analysis program:

MASTAN2

For those without Matlab, there is a compiled version (also free).