Subject: Linear Algebra
Recommendation: Introduction to Linear Algebra by Gilbert Strang
Reason: Strang presents the subject so clearly and intuitively that you feel like an expert on the subject after reading each chapter. It is by the far the best textbook I have encountered.
He is also an excellent teacher and offers the lecture notes to the corresponding MIT class online.
Book: http://www.amazon.com/Introduction-Linear-Algebra-Fourth-Edi...
Lecture: http://ocw.mit.edu/courses/mathematics/18-06-linear-algebra-...