arXiv.org: Over 383,443
(and growing daily) free papers in Physics, Mathematics, Computer
Science and Quantitative Biology.
General References
wikipedia:
This is an excellent source of (almost always) reliable information
about an incredibly wide variety of topics. Wikipedia often has
very clear, not too technical explanations technical terms.
mathworld:
Lots of good information here, often at rather technical level.
Networks and Graphs
M.E.J Newman, Models of the Small World: A Review. http://arxiv.org/abs/cond-mat/0001118/.
Published in: J. Stat. Phys. 101, 819-841 (2000). A short review
article about empirical results and different models of small world
graphs.
A list of
papers authored by members of Duncan Watts' research group.
M.E.J Newman, The structure and function of complex networks. http://arxiv.org/abs/cond-mat/0303516/.
Published in SIAM Review 45, 167-256 (2003). An excellent, clear,
and thorough review article about complex networks.