Online archives and journals

arXiv.org e-Print Archive
Electronic Colloquium on Computational Complexity
American Physical Society Journals
Quantum Information and Computation
SIAM Journals
IEEE Xplore
ACM Digital Library

Bibliographic Tools

MathSciNet
Computer Science Bibliographies
CiteSeer
Google Scholar

Other Useful Pages and Tools

ACM SIGACT
On-Line Encyclopedia of Integer Sequences
Inverse Symbolic Calculator
History of Mathematics
The Complexity Zoo
Scirate