ZINC15
    A useful database of virtual molecules which can also be organized by vendors.  We use this database in conjunction with others to build our virtual libraries.

SDBS
    The Spectra Database for Organic Compounds.  An excellent resource to find spectra for organic molecules.

NMRDB.org
    Free NMR prediction program.  Can simulate both 1H and 13C NMR.

Bordwell pKa Tables
    Contains extensive pKa values for organic molecules in DMSO.  Organized by functional groups.

Named Organic Reactions
    A useful page found on the Organic Chemistry Portal.  Contains mechanisms and references for most named reactions.

Protein Database (PDB)
    A repository for crystal structures of more than 100,000 proteins.