"247 web usability guidelines
Although designing usable systems requires far more than simply applying guidelines, guidelines can still make a significant contribution to usability by promoting consistency and good practice. We use this list of guidelines in our consultancy work. For best results, remember to interpret the guideline in context - this requires a bit more thought but ensures you will get a lot more from your review."
The US government web design and usability guidelines - HUGE book in PDF format with many guideline explained in a concise format. It's actually pretty good. I wish it was in a better format - PDF isn't the most... um, whats the word I'm looking for - USABLE format. just sayin