Open Access -
arXiv.org - Open access to e-prints in Physics, Mathematics, Computer Science, Quantitative Biology and Statistics. Cogprints - archive for self-archive papers in any area of Psychology, neuroscience, and Linguistics, and many areas of Computer Science, Philosophy, Biology, Medicine, Anthropology, as well as any other portions of the physical, social and mathematical sciences that are pertinent to the study of cognition.
Networked Computer Science Technical Reference Library - a collaborative project involving NASA Langley, Old Dominion University, University of Virginia and Virginia Tech.
RePEc - Research Papers in Economics
NDLTD - Networked Digital Library of Theses and Dissertations (NDLT)