Chemistry

From NCBI, a platform-independent chemical structure drawing tool. Provides translation into InChI/SMILES/etc., as well as exporting to image and chemical information files (i.e. MDL, ChemDraw, ISIS, etc.).

Cn3D ("see in 3D") is a helper application for web browsers that allows viewing of 3-dimensional structures from NCBI's Entrez Structure database. Cn3D is provided for Windows and Macintosh, and can be compiled on Unix. Cn3D simultaneously displays structure, sequence, and alignment, and now has powerful annotation and alignment editing features. (from website)

ChemSpider is a free chemical structure database providing fast text and structure search access to over 35 million structures from hundreds of data sources.

NLM database of compounds, substances, and bioassays, focusing on the biological activities of small molecules. PubChem provides substance information, compound structures, and bioactivity data for small molecules in three primary databases, PCsubstance, PCcompound, and PCbioassay.