The Chicago Manual of Style Online (CMOS) is a great resource for when you have to write documents in formal English and need help with all those niggling punctuation and grammar issues. Unfortunately it is not free, and so not much use to people who only have to write these sorts of things occasionally.
What is free, however, is their Q&A page. Amazingly they also manage to make the answers interesting and occasionally witty and even sarcastic. You can sign up to a monthly email newsletter of that month’s questions.
Here’s an example:
Q. I’m editing a textbook that references a play. Should it be “Act 3,” “act three,” or “act 3”? A solution to this mystery would be greatly appreciated. I’ve looked at CMOS a hundred times for help with this issue.
A. Wow—a hundred times? If you can suggest how we can make section 8.194 more clear, we’ll try to do better in the next edition: “Words denoting parts of long poems or acts and scenes of plays are usually lowercased, neither italicized nor enclosed in quotation marks . . . act 3, scene 2.”