ChemSpider is a free structure-centric community for chemists, providing access to millions of chemical structures and integration with many other online services. ChemSpider is the richest single source of structure-based chemistry information.
Recently acquired by the Royal Society of Chemistry
Easy access to chemical and physical property data; can search by author, CAS registry number, chemical name, formula, molecular weight, structure, etc. Includes spectral data. (NIST = National Institute of Standards and Technology)
The BioActivity Summary service reports the available biological screening results for a single or a set of chemical samples. This service provide means for one to examine and compare biological outcomes across multiple biological tests. Please specify compounds using the given input methods. To retrieve specific test results, please specify bioassays.