These books and website are important and helpful for those who want to learn about design basics and be graphic designers, and can supplement any design fundamentals class.

1. Basic Visual Concepts and Principles for Artists, Architects, and Designers by Charles Wallschlaeger and Cynthia Busic-Snyder (1992)A bit dated, but thorough, with many examples.

2. Art and Visual Perception, A Psychology of the Creative Eye by Rudolf Arnheim (1954)
Excellent and often cited.

3. colorsontheweb.com
Succinct and up-to-date for color on the web. Includes several useful online tools.

4. History of Graphic Design, 4th edition, by Philip B. Meggs and Alston Purvis (2005)
The most widely-used textbook on the canon of graphic design history.

5. How to be a Graphic Designer Without Losing Your Soul by Adrian Shaughnessy (2005)
Sensitive, common-sense advice on being a creative professional.