Brand Guidelines
Hone your eye for great brand writing with these top notch brand voice, expression and verbal identity examples.

A comprehensive look at the Mailchimp voice, the rules that govern it and the nuances that make it.

A basic guidelines site for the brand but it includes everything from writing to illustration to marketing. The writing section goes deeper than most with sample messaging, audience-specific messaging, persona and more.
The luxury automaker showcases their brand elements in a simple site experience. There voice and tone section is definitely worth checking out.

The verbal identity guidelines for online bank Monzo is right on the money.

Firefox puts it all out there for public view -- including their positioning, persona, tone of voice and full design kit of parts.

Shopify has a very thoughtful breakdown of their verbal identity and content that spans everything from language to grammar to tone to naming.

A comprehensive guideline for all things Dropbox including strategy (a rare public find), brand system, and writing principles.

A comprehensive guideline that covers literally everything about the brand -- history, guidelines, resources, usage, even the story behind their tagline. A very thoughtful example of an external brand book.