You might wish to consult also other lists and collections
Particularly recommended: Project Gutenberg Physics and Astronomy sections.
 

Free, online Physics BOOKS

• A Cicerone for the Physics of Charm
  by S.Bianco, F.L.Fabbri, D.Benson and I.Bigi (on arXiv).
• Algebraic Quantum Field Theory by Hans Halvorson and Michael Mueger (on arXiv).
• A Revised Electromagnetic Theory with Fundamental Applications
  by Bo Lehnert in Progress in Physics. Speculative physics.
  Svenska Fysikarkivet, Stockholm, 2008, ISBN 978-9185917006.
• Basic Bundle Theory and K-Cohomology Invariants, by D.Husemöller et al.
  Available also in printed version
• Calculus-Based Physics by Jeffrey W.Schnick.
• Champs, Vide, et Universe Miroir, in French,
  by Larissa Borisova and Dmitri Rabounski in Progress in Physics.
  American Research Press, Rehoboth (NM), 2010, ISBN 978-1599731230.
• Chronometric Invariants
  by Abraham Zelmanov in Progress in Physics. Speculative Physics.
  American Research Press, Rehoboth (NM), 2006, ISBN 1599730111.
  Russion version: ISBN 159973012X.
• Cosmic Physical Factors in Random Processes, in Russian,
  by Simon E.Schnoll in Progress in Physics. Speculative physics.
  Svenska Fysikarkivet, Stockholm, 2009, ISBN 978-9185917068.
• Data Analysis of Gravitational Waves by S.K.Sahay in Progress in Physics.
  Svenska Fysikarkivet, Stockholm, 2008, ISBN 978-9185917051.
• DOE Fundamentals Handbooks (DOE stands for the US Department of Energy):
     Classical Physics
     Instrumentation and Control, Volume 1 and Volume 2.
     Thermodynamics, Heat Transfer, and Fluid Flow, Volume1, Volume 2, Volume 3.
     Mechanical Science, Volume 1 and Volume 2.
     Nuclear Physics and Reactor Theory, Volume 1 and Volume 2.
• Dynamical Systems by George D.Birkhoff (AMS 1927).
• Dynamical Theories of Brownian Motion by Edward Nelson.
• Elements for Physics: Quantities, Qualities, and Intrinsic Theories by Albert Tarantola.
  Springer 2005. Printed version also available.
• Encyclopedia of Physics edited by A.M.Prohorov et al (1988). DJVU format. In Russian.
• Eppur si muove by Stefan Marinov in Progress in Physics. 3rd Edition. Speculative physics.
  East-West Publishers, Graz 1987. Also available in DjVu format. Pending:
  4th Edition, North European Scientific Publishers, Hanko (Finland, ISBN 978-9526734965).
• Feynman Lectures on Physics by Richard P.Feynman, R.B.Leighton, and M.Sands, at CalTech.
• Field Theory by Predrag Cvitanovic'.
• Fields by Warren Siegel (on arXiv).
• Fields, Vacuum, and the Mirror Universe
  by Larissa Borissova and Dmitri Rabounski in Progress in Physics. Speculative physics.
  Svenska Fysikarkivet, Stockholm, 2009, ISBN 978-9185917099.
  New, expanded edition is available in Russion (2010, ISBN 978-9185917112).
• Final Book on Fundamental Theoretical Physics by Gunn Quznetsov
  in Progress in Physics.
  American Research Press, Rehoboth (NM), 2011, ISBN 978-1599731728.
• Introduction to Continuum Mechanics for Engineers by Ray M. Bowen.
  2008 update of the 1st Edition by Plenum Press in 1989.
• Introduction to Groups, Invariants & Particles by Frank W.K.Firk.
• Inverse Problem Theory and Methods for Model Parameter Estimation
  by Albert Tarantola, SIAM 2005. Printed version also available.
• Linear Methods of Applied Mathematics by E.M.Harrell II and J.Herod.
• Mapping of Probabilities - Theory for the Interpretation of Uncertain Physical Measurements, by Albert Tarantola. In preparation, but two large Chapters are finished.
• NIC Symposium 2006, NIC Volume 32, Proceedings edited by Münster et al.
  High-end scientific computing, including Physics.
• NIC Workshop: From Computational Biophysics to Systems Biology 2006, NIC Volume 34,
  Edited by U.H.E.Hansmann et al. Proceedings of CBSB06.
• Particles Here and Beyond the Mirror
  by Dmitri Rabounski and Larissa Borissova in Progress in Physics. Speculative physics.
  Svenska Fysikarkivet, Stockholm, 2008, ISBN 978-9185917037.
• Photonic Crystals: Molding the Flow of Light, a textbook
  by John D.Joannopoulos, Steven G.Johnson, Joshua N.Winn, and Robert D.Meade.
  Preprint. You can purchase the final printed version.
• Photophysics of Conjugated Polymers and Fullerenes, edited by Niyazi Serdar Sariciftci.
• Poincaré Seminaire (Bourbaphy). French & English contributions.
  I: L'Énergie du Vide. Vacuum Energy.
  II: La Renormalisation. Renormalization.
  III: La Condensation de Bose-Einstein. Bose-Einstein Condensation.
  IV: L'Entropie. Entropy.
  V: La Théorie des Cordes. String Theory.
  VI: L'Effet Hall Quantique. Quantum Hall Effect.
  VII: Einstein 1905-2005. Einstein 1905-2005.
  VIII: Décohérence Quantique. Quantum Decoherence.
  IX: Gravitation & Expérience. Gravitation and Experiment.
  X: Espaces Quantiques. Quantum Spaces.
  XI: The Spin. The Spin. Printed version: Birkhäuser Basel 2009. ISBN 978-3764387983.
  XII: Bio-Physique. Physics and Biology.
  XIII: Werres & Graines. Glasses and Granular Materials.
  XIV: Le Chaos. The Chaos.
  XV: Le Temps. Time.
• Quantum Field Theory by Mark Srednicki. Available also in printed version.
• Quantum Fluctuations by Edward Nelson.
• Quantum Mechanics in Chemistry by Jeff Simons and Jeff Nichols.
• Quantum Monte Carlo methods for the solution of the Schroedinger equation for molecular systems by Alán Aspuru-Guzik and William A.Lester Jr.
• Quantum Simulations of Complex Many-Body Systems: From Theory to Algorithms, NIC Volume 10, edited by J.Grotendorst et al.
  Lecture Notes of a Winter School, Feb.25-Mar.1 2002, Kerkrade, Netherlands. There are also the event's poster presentations (NIC Vol.11) and audio-visual lectrure notes (NIC Vol.14).
• Spin-Curvature and the Unification of Fields in a Twisted Space
  by Indranu Suhendro in Progress in Physics. Speculative physics.
  Svenska Fysikarkivet, Stockholm, 2008, ISBN 978-9185917013.
• Strongly Disordered Quantum Spin Systems in Low Dimensions: Numerical Study of Spin Chains, Spin Ladders and Two-Dimensional Systems, NIC Volume 12, by Yu-Cheng Lin.
• The Grand Unified Theory of Classical Physics by Robert L.Mills, in DjVu format.
  Blacklight Power 2007. Three Volumes: A) Atomic Physics, B) Molecular Physics,
  and C) Collective Phenomena, High-Energy Physics and Cosmology.
• Topics in Dynamics I: Flows by Edward Nelson.
• Upper Limit in Mendeleev's Periodic Table - Element No.155
  by Albert Khazan in Progress in Physics. New, updated version.
  Svenska Fysikarkivet, Stockholm, 2010, ISBN 978-9185917105.

Free, online books RELATED to Physics

• A New Kind of Science by Stephen Wolfram (first printed in 2002).
  Software, math and physics. Page-by-page access.
• Chaos: Classical and Quantum by Predrag Cvitanovic'.
• Consciousness, Physics, and the Holographic Paradigm by A.T.Williams.
  Unusual, stuffed with links and poetry. Worth pondering.
• From Computational Biophysics to Systems Biology (CBSB07), NIC Volume 36,
  Edited by U.H.E.Hansmann et al. Proceedings of CBSB07.
• Geophysical Tomography. North Holland 1990, Edited by Albert Tarantola.
• Mathematical Tools for Physics by James Nearing.
• Mechanism of the Heavens by Mary Somerville (1831),
  made available by Malaspina Great Books. 2nd Edition, prepared by Russell McNeil.
• Motion Mountain: The Adventure of Physics by Christoph Schiller. Introductory & good.
• Symmetry Rules: How Science and Nature are Founded on Symmetry
  by Joe Rosen (Springer 2008).
• The Age of Einstein by Frank W.K.Firk.
• Theory of the Earth by Don L.Anderson.

Free, online Physics Courses, Lecture Notes and Textbooks

• A Spectroscopy Companion course by Masaru Kuno (2006).
• Conceptual Physics, a college textbook by B.Crowell. (Creative Commons 2008).
• Conservation Laws, a college textbook by B.Crowell. (Creative Commons 2008).
• Discover Physics, a college textbook by B.Crowell. (Creative Commons 2008).
• Electricity and Magnetism, free MIT course (Physics 8.02). Excellent.
• Electricity and Magnetism, a college textbook by B.Crowell. (Creative Commons 2008).
• Electromagnetic Field Theory, a textbook by Bo Thidé. With exercizes.
• Essential Physics I textbook by Frank W.K.Firk.
• Introduction to Statics and Dynamics by Rudra Pratap and Andy Ruina. Attention: for Cornell University class use only!
• Lecture Notes on General Relativity by Sean M.Carroll (on arXiv).
• Lecture Notes in Quantum Mechanics by Doron Cohen.
• Lectures in Physics, a course derived from B.Cromwell's free texts.
• Lectures on Quantum Physics and Applications by Paul E.Dimotakis.
• Macroscopic Electrodynamics, a graduate textbook by Walter Wilcox. Two Volumes.
• Mathematical Methods in Quantum Mechanics; With Applications to Schrödinger Operators, a textbook by Gerald Teschl.
• Modern Introductory Mechanics, a textbook by Walter Wilcox. Two Volumes.
• Modern Relativity, a text book tutorial on Albert Einstein's theories of special and general relativity by David Waite. Excellent!
• Newtonian Physics, a college textbook by B.Crowell. Creative Commons 2008.
• Optics, a college textbook by B.Crowell (Creative Commons 2008).
• Physical Description of Chemical Systems, lecture notes by Geoffrey A.Blake.
• Physics lectures by Fritz Bosch. A few are in English, most in German
• Quantum Mechanics, a textbook by K.Schulten.
• Quantum Mechanics, a basic course for chemists by Masaru Kuno (2008).
• Quantum Mechanics and Spectroscopy, a workbook for chemists by Masaru Kuno (2004).
• Quantum Principles and Particles, a textbook by Walter Wilcox.
• Simple Nature, Volume 1 and Volume 2, college textbooks by B.Crowell (CC 2008).
• Topics in Electrodynamics, an undergraduate textbook by Walter Wilcox.
• The Modern Revolution in Physics, a college textbook by Benjamin Crowell (CC 2008).
• Thermal Physics course by Michael Gershenson (Rutgers Uni).
• Thermodynamics, lecture notes by Zoltan S.Spakovszky (MIT). Exhaustive and excellent.
• Thermodynamics & Statistical Mechanics, lecture notes by Richard Fitzpatrick (Uni Texas at Austin). Very extensive, HTML only.
• Vibrations and Waves, a college textbook by Benjamin Crowell (Creative Commons 2008).
• Video Lectures on The Best Physics Videos.
• What is String Theory by Joseph Polchinski (on arXiv).

Free, online Physics THESES

Consult also CERN Document Server with its special section reserved for Theses.

• 2009 Peter E.Diehr, PhD, University of Michigan, USA
  An Ultrafast Photo-Electron Diffractometer.