Open Educational Resources: Computer Science

Database Design 2nd Edition - covers the concepts used in database systems and the database design process.

Foundations of Computation - includes topics from discrete mathematics, automata theory, formal language theory, and the theory of computation, along with practical applications to computer science.

An Introduction to Computer Networks - general-purpose computer-networking textbook, complete with diagrams and exercises. 

Short Online Courses

Principles of Computing with Python  - Developed by Carnegie Mellon University. This course requires users to create an account to save work.  The course provides an introduction to Python and elementary principles of computing, including iteration, recursion, and binary representation of data. Additional topics on cellular automata, encryption, and the limits of computation are also introduced.