A Japanese counterpart to PubChem/PubMed. One of the most interesting services on this list, KEGG consists of four interconnected databases: KEGG Pathway; KEGG genes; KEGG Brite; and KEGG Ligand. KEGG Ligand contains over 14,000 compounds searchable by name, and crosslinked to over 45,000 biological pathways. The KEGG Ligand database can be searched by structure through KegDraw, a 2-D structure editor written in Java. With some minor configuration on my Linux system, I was able to perform some basic substructure searches using KegDraw. Your mileage may vary. A nice overview of KEGG is available in a recent article. The contents of KEGG can be downloaded by anonymous ftp for academic use.