History

Einstein, Nordström and the Early Demise of Scalar, Lorentz Covariant Theories of Gravitation
About the development of general relativity, Einstein's early rejection of Lorentz-covariant theories of gravity, and Nordström's attempts at formulating just such a model. By J. D. Norton (University of Pittsburgh). [PDF]
http://www.pitt.edu/~jdnorton/papers/Nordstroem.pdf

Einstein's Articles in "Annalen der Physik"
Website by the Max Planck Institute for the History of Science (Berlin) presenting the seminal articles on relativity and other subjects that Einstein published in the physics journal "Annalen der Physik"; also includes four introductory essays based on recent historical studies.
http://einstein-annalen.mpiwg-berlin.mpg.de/home

Einstein's Discovery of Relativity
Essay by John Stachel (Boston University) which gives a concise account of Einstein's biography at the turn of the century, and attempts to reconstruct how he developed the special theory of relativity.
http://www.aip.org/history/einstein/essay-einstein-relativity.htm

Einstein's Time
A discussion of the differences in perspective between Einstein and Poincaré between Peter Galison (Harvard) and Graham Burnett (Princeton); main focus are the notions of time and simultaneity.
http://www.aip.org/history/einstein/essay-einsteins-time.htm

Henri Poincaré and Relativity Theory
Identifies the contributions made to the special theory of relativity by Poincaré and argues that the theory "has been created not by A. Einstein only but even to a greater extent by Poincaré." By A. A. Logunov. [PDF]
http://arxiv.org/abs/physics/0408077

History of General Relativity
Wikipedia article on the development of relativity. Includes sections about observational tests and alternative theories.
http://en.wikipedia.org/wiki/History_of_general_relativity

History of Special Relativity
Wikipedia article on the genesis and development of special relativity and its precursors.
http://en.wikipedia.org/wiki/History_of_special_relativity

History Topic: General Relativity
An outline of the development of the theory, including a summary of relevant earlier work (from Aristotle to Maxwell); from the MacTutor History of Mathematics Archive (University of St. Andrews).
http://www-history.mcs.st-andrews.ac.uk/HistTopics/General_relativity.html

History Topic: Special Relativity
Concise summary of the history of special relativity, from Maxwell and Lorentz to Einstein; from the MacTutor History of Mathematics Archive (University of St. Andrews).
http://www-history.mcs.st-andrews.ac.uk/~history/HistTopics/Special_relativity.html

A Note on Relativity before Einstein
The first presentation of the Lorentz transformations, including the crucial time dilation, belongs to Larmor (c. 1897). [PDF]
http://eprint.uq.edu.au/archive/00002307/01/larmor.pdf

Of Pots and Holes: Einstein’s Bumpy Road to General Relativity
Article tracing the history of general relativity, by the historian of science Michel Janssen (University of Minnesota). [PDF]
http://www.tc.umn.edu/~janss011/pdf%20files/potsandholes.pdf

Olinto De Pretto
Wikipedia article about the Italian industrialist and claims that he published the famous formula E=mc² two years before Einstein did.
http://en.wikipedia.org/wiki/Olinto_De_Pretto

Relativity Priority Dispute
Wikipedia article about the various contributors to special and general relativity, and about the contentious questions of who has priority on the different ideas and concepts involved, and in how far Einstein was influenced by his contemporaries and predecessors.
http://en.wikipedia.org/wiki/Relativity_priority_dispute

Scott Walter's Homepage
Contains articles of the historian of science Scott Walter (Université de Nancy 2), including those on the history of special relativity, with a special focus on contributors other than Einstein (such as Poincaré, and Minkowski). [PDF]
http://www.univ-nancy2.fr/DepPhilo/walter/

Lost in Einstein's Shadow
American Scientist magazine article describes the people whose work paved the way for the special theory of relativity. By Tony Rothman; also includes link to PDF version. <small>(March, 2006)</small>
http://www.americanscientist.org/issues/pub/2006/2/lost-in-einsteins-shadow

Einstein and Hilbert: The Creation of General Relativity
Discusses the correspondence between the two, their priority dispute, and their amicable resolution of it. By Ivan T. Todorov. <small>(April 25, 2005)</small>
http://arxiv.org/abs/physics/0504179

Eclipse Showed Gravity Vatiation
New York Times article on the 1919 eclipse observations by two British expeditions, which confirmed the predictions of general relativity for light deflection near the sun. [PDF] <small>(November 9, 1919)</small>
http://query.nytimes.com/mem/archive-free/pdf?res=950DE7D61138EE32A2575AC0A9679D946896D6CF