Free Textbook Collection
Abstract Algebra: Judson's book
Linear Algebra: Breezer's book, Kuttler book
Differential Equations: Trench's book
Discrete Math: Levin's book, Doerr and Levasseur
Multivariable Calculus: Active Calculus
Probability: Intro to Probability and Statistics
Math for Trades: Technical Mathematics
Math for Liberal Art: Contemporary Math