I rather like the following:

• Refactoring: improving the design of existing code by Martin Fowler
• The art of objects: object-oriented design and architecture by Yun-Tung Lau
• Introduction to the theory of computation by Micheal Sipser
• Real Computing made Real: preventing errors in scientific and engineering calculations by Forman S. Actor
• Numerical Recipes in C by William H. Press, Brian P. Flannery, Saul A. Teukolsky, William T. Vetterling (note: this one is available online as well)
• Elements of Information Theory by Thomas M. Cover and Joy A. Thomas
• An introduction to databases systems by C.J. Date

and problebly I forgot a lot ;-)

Tell me what you read and I'll tell you who you are, -gjb-