Last week, the Princeton University Press published the
Digital Einstein Papers, electronic versions of an enormous number of Albert Einstein's written works, including published papers, popular writings, and even personal correspondence with scientists and family.
The site presents all 13 volumes published to date by the editors of the Einstein Papers Project, covering the writings and correspondence of Albert Einstein (1879-1955) from his youth to 1923.
The volumes are presented in the original language version with in-depth English language annotation and other scholarly apparatus. In addition, the reader can toggle to an English language translation of most documents.
This is an incredible collection. An enormous amount of work has been put in by both projects to collect and translate the works. If you find any documents of particular interest, post a link in the comments!