ChemDatabaseService - YouTube
The National Chemical Database Service, which is funded by the EPSRC and hosted by the Royal Society of Chemistry have produced a series of webinars about their (non-crystallography) databases.
SPRESIweb is a structure and reaction database for organic chemists. It contains 5.52 million molecules and 4.26 million reactions extracted from the literature by VINITI (USSR) from 1974.
ARChem is another tool for the synthetic organic chemist. It takes a database of reactions and uses it to generate a set of rules for finding synthetic pathways. In this case, the database used is the RSC's 'Methods in Organic Synthesis’.
ACD/i-Lab2 You can search by compound name or structure (draw or import). It contains experimental property data from the literature and predicted data, including spectra and log P.
Chemicalize is a free web application where you can type in a URL and it will augment the web page, pulling out any chemical structures.