Scientific literature searches: Web of Science
Google Scholar
Nanotechnology lectures, software online: Nanohub
EMSL Basis Set Library
Online theory/science books/courses:

Sherrill Group Notes - QC
Simons and Nichols - QC Electronic Materials
MIT Open CourseWare

Linux (and more) software:

SourceForge
The Gnu Project
CTAN (The Comprehensive Tex Archive Network)

For (often good citations to) anything: Wikipedia