Chemguide: Helping you to understand Chemistry (Jim Clark, 2004)
The Sheffield Chemdex: the directory of chemistry on the WWW since 1993 (Sheffield Univ)
Wired Chemist (Claude Yoder)
ChemFinder (Cambridgesoft, commercial)
Reaxys (Elsevier, commercial)
CRC Handbook of chemistry and physics, ed W M Haynes, D R Lide, T J Bruno (CRC) – e2017, online
Lange's Handbook of Chemistry, ed J Speight (MGH, 2004), 16ed
IUPAC nomenclature (Wikipedia)
Introductory Chemistry (Iwanami Shoten, 2004-2006)
Tutorial chemistry text (Royal Society of Chemistry, 2000-2004)
General Chemistry: Lecture Notes (Course, Univ of Texas, 1996)
compoundchem.com: Alcohol chemistry, Aroma chemistry etc.
R H Petrucci, F G Herring, J D Madura, C Bissonnette, General chemistry: principles and modern applications (Pearson, 2017), 11ed