This is a quick response to a question from a student about style guides.
It’s just a ist of the ones I’d say were the most useful and/or interesting.
Yahoo! Style Guide
(excellent guide to writing for the web; covers everything from basic grammar to tips on SEO.)
Reuters Handbook of Journalism
(searchable; section headings)
The Economist Style Guide
Clunky page, but this is my favourite. I’d recommend buying the book.
Financial Times Lexicon
The Times Style and Usage Guide
(section headings; alphabetical links)
Telegraph Style Book
(section headings and alphabetical links)
Guardian online style guide
BBC style guide
(useful for broadcasters and writers)