LocalGovDigital has some great advice on writing for the web. It starts with their golden rules, rule 1 being Is the information you’re presenting to the public necessary, readable, original, easy to find and well-presented? There’s advice on grammar and presentation, all very familiar from my past life in publishing.
Intercom stress being authoritative and human, and using the the 5 Ws: who, what, where, when, why
Bruce's IT-ish world 