The Mighty Wiki
Style Guide (The Short Version) — This has the basics of what you need to know to write, format, and create new content.
Style Guide (Long Version) — This has everything on style, grammar, copy-edits, headlines, etc.
Vertical Guidelines — What goes where. Why it goes there. What fits in with our brand.
How To Make Great Slideshows — Self-explanatory.
Social Media Posts — Best practices for posting to social networks.
Instant Messenger Handles: The mass listing of how to best reach everyone for real-time comms.