A great resource for classroom teaching and lifelong learning: a freely downloadable physics textbook that spans over the fundamentals of the field with an eye on the recent research:
The project aims to produce a simple, vivid and up-to-date introduction to modern physics, with emphasis on the fundamental ideas of motion. ‘Simple’ means that concepts are stressed more than formalism; ‘vivid’ means that the reader is continuously challenged; ‘up-to-date’ means that modern research and ideas about unification are included.
The project takes the search for a precise description of motion as a guiding principle for an exploration of modern physics. This leads to an approach which is somewhat different from the standard one. Nature’s limits to speed, entropy, force, action and charge are central to the presentation.
Other physics textbooks online:
The high-quality electrodynamics text by Bo Thidé, Electromagnetic Field Theory, can be found at http://www.plasma.uu.se/CED/Book, together with its collection of exercises.
There are also the excellent introductory physics texts by Benjamin Crowell, Simple Nature and Light and Matter, which can be downloaded at http://www.lightandmatter.com.
The interesting Biophysics Educational Resources, edited by Victor Bloomfield, can be found at http://www.biophysics.org/education/resources.htm.
The text Classical and Quantum Chaos, edited by Predrag Cvitanovic, Roberto Artuso, Per Dahlqvist, Ronnie Mainieri, Gregor Tanner, Gábor Vattay, Niall Whelan and Andreas Wirzba can be found at http://chaosbook.org.