Mathphysics.com - This site exists primarily to host on-line textbooks and other scholarly materials in mathematics or physics.

Online Texts - Links to online mathematics texts, maintained by George Cain at Georgia Institute of Technology.

AMS Books Online - AMS published books available for free download in PDF. Also links to other online books.

Mathwright Library - A free collection of interactive mathematics and science books. Requires free (Windows) software to read.

arXiv - E-print archive in various areas of physics, mathematics, nonlinear science, and computer science.

Cornell Digital Library Math Collection - 571 books that were scanned from originals held by the Cornell University Library. Each page is a GIF image.

EMIS Mathematical Monographs - Books hosted by the European Mathematical Information Service in various formats, typically PostScript, but sometimes also DVI and PDF.

Tempus - Modules for applied mathematics, including modelling, discrete simulation, linear algebra, harmonic analysis and optimization. HTML with embedded GIFs. Some modules available in PostScript and in Estonian.

EJDE Monographs - Textbooks and expository articles hosted by the Electronic Journal of Differential Equations.

ICTP Lecture Notes Series - Paedagogical material in advanced topics from the Abdus Salam International Centre for Theoretical Physics, Trieste. LaTeX and PostScript.

Mathematics Archives - Topics - Links to books, notes and other resources organized by topic at the University of Tennessee, Knoxville.

Mathematics lecture notes - Lecture notes collected by Matt Daws.

Online Books and Lecture Notes in Mathematics - Collection of links at gotmath.com

Electronic Books and Journals - Links maintained by the University of Haifa.

Geometry & Topology Monographs - A series intended for research monographs, for refereed conference proceedings, and for similar collections.

Birkhäuser Online Reading Room - Texts in Mathematics and Statistics. Full text in GIF format.