Websites with a contemporary approach:
Adam Auton: Visual Appearance of Objects at Relativistic Speeds
~ Download/observe a simulator of the visual appearance of objects moving at relativistic speeds
Sylvain Poirier: Special Relativity Theory Made Intuitive (French, English)
C. E. Harle, R. Bianconi: Special Relativity and Geometry
M. Erk Durgun: Geometric Generalization of the Structure of Nature
~ A conceptual theory which generates Relativity and Quantum Mechanics.
Nassim Haramein, E.A. Rausher: Scientific papers and articles
~ Spin, torque, Coriolis forces in Einstein's field equations and grand unification theory.
Brian Sowards: New Relativity
~ Explores relativistic paradoxes and thought experiments with emphasis on force and acceleration.

Websites Critical of Relativity
Erik J. Lange: Proof of the Falsity of the Special Theory of Relativity
~ Presents an error in the proof of the Lorentz transformation equations.
Joseph Rybczyk: Millennium Relativity
~ An alternative to the commonly accepted theory.
G. Walton: Reclaiming the Common Sense Foundations of Knowledge
~ Articles, extensive list of dissidents to contemporary physics
Rob Van Linden: Dimensions in Special Relativity (PDF/Postscript downloads)
~ proposes an Euclidean interpretation of special relativity, and interpretations of other physical concepts in terms of dimensions

Cameron Rebigsol: Relativity Mathematically Fails
~ Reward of $50,000 offered for refuting his text, "Mathematical Invalidity of Special Relativity"
JeanDavid: Special Relativity
~ Argument against Special Relativity by the deviation of light direction with speed
Sergey N. Arteha: Criticism of the Foundations of Relativity Theory
E.A. Robinson: General Theory of Relative Motions
~ Reinterpretation of the Doppler effect to explain the result of the Michelson-Morley experiment et al.

Milan R. Pavlovic: Einstein's Theory of Relativity ~ Related Subjects
E. Dowdye: Most Recent Emission Theory. A Pure Classical Alternative to Relativity
David Kemp: Relativity, Space-Time Emotional Exercises
Marcelo Crotti: Introduction to the Concepts of Relativity
~ Concepts, foundations and critical analysis (partially tranlated from Spanish), accepts the Lorentz formulas but criticizes its interpretation.

Christos A. Tsolkas: Experiments and Papers
Jose Ledesma: Papers on Special Relativity (Spanish, English)
~ Claim that Relativity theory reintroduced the ether while keeping it at the same time, eradicating logic from science in the last century, whereas Newton's laws without ether explained everything.
C. Kingston: Light, The Enigma
Special Theory of Relativity "A quick guide for cranks"
~ Visitors can vote, comment on, debate on whether SR is "profound" or "cheesecake"
Frank G. Pearce: Test of Relativity Theory
~ Theory regarding transmission of electromagnetic energy in vacuo by a field medium.

Jorgemanuel: Concepcion Logica de la Teoria de la Relatividad (Spanish Text)
Gennady Sokolov, Vitali Sokolov: Experimental Disproof of Special Relativity
Aleksandar Vukelja: Elementary Concepts in Physics
~ Demonstrates invalidity of Lorentz transformations and relativity theory
Andrija Radovic: Relativity Theory, Electrodynamics, Physics
~ Derivation of the equations of relativity from classical electrodynamics

G. Burniston Brown What is Wrong with Relativity?
~Historical perspectives.
Michelson H. Morley: Classical v/s Mystical Reality
~ Refreshing look at Special Relativity et al.
T. Stanton: Theory of True Relativity
~ Critique of relativity and alternate theory. Offer of £500 reward to first person who can disprove theory and math of true relativity.
Curt Renshaw: The radiation continuum model (RCM)
~ Provides a comprehensive alternative to the special and general theories of relativity based on Galilean-Newtonian physics.
Ajay Sharma: Debate on the Basic Laws of Science
~ Critical analysis of relativistic energy equations.
Stephen J. Crothers: Published Papers
~ Critical analysis of special and general relativity.
Jocelyne Lopez: Blog: Relativity Theory, German Text Only

Cosmology - Astrophysics:

Carel van der Togt: Ether Theory, Related Subjects-Physics
Dr. Randy Frid: Physics Papers
Eit Gaastra: A Different View on Cosmology
Anatolij V. Rykov: The Physical Vacuum and the Unity of Nature
James DeMeo: Analysis of Dayton Miller's Aether Drift Experiments/Shankland Critique
Meta Research: Challenges to Mainstream Astronomy
Jack Martinelli: The Sub-Space Project
Webster Kehr: The Detection of the Ether (PDF Download Available)
Colin Hill: Fractal Universe Hypothesis
Guido Grzinic: An Alternative Theory of the Universe Based on Hyperdimensional Aether
Dragan N. Turanyanin: Wave Cosmodynamics
Marco Pereira: Hypergeometrical Universe: The Theory of Everything
V. M. Antonov: Theory of Ether Physics Russian Language Only
Andrezej Karon: The Moons of the Solar System
Meta Research: Astronomy - Scientifically viable challenges to mainstream paradigms
Dr. Alfredo Bennun: Collected Papers, Cosmology, Biophysics

Mechanics and Electrodynamics

Harry Yosh: : Wave Equation
D. Ramakuri: : The Nature of Light
Alan Cresswell: Physics Papers
Ivor Catt: Electromagnetism, Books, Articles, Commentary

D. Sarkadi & L. Bodonyi: Gravity Experiment Between Commensurable Masses
D. Sarkadi: A New Physical Model for the Atomic Mass Calculation (PDF)
Nigel Cook: Gravity, Electromagnetism
Gary Novak: An Error in the Equation for Kinetic Energy

Branko Miscovic: Neoclassical Electrodynamics (Downloads, PDF format)
L. Gaasenbeek: Helical Particle Wave Theory/Selected Papers
Alejandro A. Torassa: On a New Dynamics
Electrogravity Physics: Gravitational Theory

Dilip James: Electromagnetics ~ Grand Unified Theory
Emory Taylor: The Loophole Hypothesis
G. D. Niplokov: Inertial Mechanics
J. J. Smulsky: Mechanics, Electrodynamics, Theoretical Physics

Newton's Castle: Site dedicated to the works of Sir Isaac Newton
Timm A. Vanderelli: Study of static magnetic fields with images
Physclips: Classical mechanics with animations and film clips
G. L. Abramyan: Analysis of the dynamics of the solar system
Yuri Rylov: Theoretical Physics ~ Problems in Mechanics
Maria Kovalenko: Physics Laboratory Interactive Simulations ~ Animation in real time
Eric Sabo: Gravity and the Unified Theory

Mathematical Physics:

Prof. U. Bartocci: Foundations of Physics - Mathematics - Epistemology (Italian/English)
Dr. R. M. Kiehn: Cartan's Corner
D.E. Matthieu Laudat: Challenging Theories and Fields - Collected papers

Science Directories

Ondwelle Publications Interdisciplinary Attack on Unexplained Aspects of Mind, Brain, Nervous System
Hyperspace at QMW International Society on General Relativity and Gravitation
Spacetransportation Science Direcory: Extensive listings of scientific subjects
Science Links:Links to a broad selection of scientific sites
General Physics: Physics, Astronomy Links and Resources
Nature Quest: Science Forum - Debates
Geometry: The Online Learning Center Reference Materials and Links to Maths, Sciences, Philosophy
Lucol: Extensive Collection of Scientific Sites, Forums, Facilities
Science Daily: Latest Discoveries, Research Projects in All Fields of Science
World Science Online Science Magazine S.O.S. Mathematics: Mathematical Resources: Algebra, Geometry, Calculus, etc.