Mathematical Literature

A very useful guide to mathematics on the internet is the American Mathematical Society, AMS. If you are logged on to a server subscribing to MathSciNet you have access to a comprehensive database of mathematical literature. If you are looking for mathematical articles you can probably find what you are looking for at the arXiv. Another great place to look for mathematical literature is the library at the Department of Mathematics, Aarhus University.

The following links contain notes and free books from the internet. I do not know whether the books are of good quality or not.
Free books,
University of Heidelberg notes

Allen Hatcher has writen some very readable books on various topic in algebraic topology. You an download the files on his webpage.

A list of some of the bachelor projects written at the Department of Mathematics, Aarhus University can be found here, Bachelor projects.

Below you find links to some of the publishers of mathematical literature.

Springer-Verlag
Springer-Verlag New York
Springer-Lange Antiquariat
Pearson Education Includes Addison-Wesley Longman Publishers
American Mathematical Society bookstore
Birkhauser Verlag
Cambridge University Press
Kluwer Academic Publishers
Oxford University Press
John Wiley and Sons
Lecture notes series, Aarhus