Protein Data Bank - Publicly available crystal structures of protein and protein/ ligand complexes.  Many protein sequence tools and links to other databases are available on this site.

Entrez - The Life Sciences Search Engine - This Entrez link provides access to their cross-database search page.  Use this if you are looking for a multi-database search:  PubMed, PubMed Central, books, genome sequences, protein sequences, 3-D structures, taxonomy, SNPs, and much more.  Worth a visit.

ACS (American Chemical Society) - Main ACS home page.  Access to all things ACS.

ACS Meetings - Direct link to past, present and future ACS meetings.  Conferences, local and division meetings, career development, short courses, continuing education, and more.

PubChem - Information on the biological activities of small molecules.  It is a component of NIH's Molecular Libraries Roadmap Initiative. Search using chemical structures, SMILES, MOL files, names, synonyms or keywords.  Search bioassay records.  (descriptions paraphrased or verbatum from their site)