Some useful and whimsical links:

MIT Department of Biological Engineering.
The MIT Homepage
The Advanced Biomedical Computing Center at NCI Frederick.
Medline (PubMed): Free access.
Wiley Base-Peak (formerly Murray's Mass Spectrometry website).
Mass spectrometry tutorials.
The Virtual Classroom from James Hardy at the University of Akron.
MIT nitric oxide page.
American Chemical Society.
ACS Division of Chemical Toxicology.
American Society for Mass Spectrometry.
EMBL Bioanalytical Research Group.
Some proteomics websites.
Skyline targeted proteomics environment
Spectroscopy Online (reviews and techniques).
Links to MANY mass spec (and other analytical) utilities.
The Human Metabolome Database at the University of Alberta (HMDB).
The Kyoto Encyclopedia of Genes and Genomes (KEGG).
Scripps Center for Metabolomics and Mass Spectrometry (METLIN).