Table of Standard Genetic Code - at Helix Systems (NIH only)
Codon Usage Tables - GenBank release 147.0 [June 1 2005], at Kazusa DNA Research Institute
General Molecular Biology Data - from New England Biolabs

Amino acid structure and properties - includes 3D interactive models, at University of Berlin
IMB - comprehensive catalog of macromolecular references, at Jena, Germany
HUGO Gene Nomenclature Committee - Giving unique and meaningful names to every human gene
The Synergizer - translates gene and protein identifiers between a huge number of databases, at Harvard Univ.
CRONOS - Cross-mapping of gene and protein identifiers between different databases, at Munich Information Center

Buffer Calculator - pick buffer parameters and put out a neat printable recipe, at EMBL-Heidelberg
Web Elements - at University of Sheffield, UK
Molecular Biology Protocols - hosted by BioTechniques
Biosafety in Biomedical and Microbiological Laboratories - 4th Edition (May 1999), CDC/NIH
Recommendations for the Safe Handling of Cytotoxic Drugs - NIH Division of Safety
IUPAC - at University of London
PCRLinks.com - very nice resource for PCR tidbits, in English and Spanish
XtalPred - Predict protein crystallizability, at JCSG
ChemSpider - Structure-based chemistry information

PubMed - the most widely used bibliographic source
Full Text Online Journals - through the NIH Library (NIH only)
Online Books - through the National Library of Medicine (NIH only)
CRISP - Computer Retrieval of Information on Scientific Projects
IHOP - A gene network for navigating the literature
Jane - semantics-based article search
FACTA - Text search engine for MEDLINE abstracts, at Univ. Manchester