And Now, for Something Completely Different: Proofreading Marks

"Proofreading Marks"
Technical Communication 6e Usage Handbook

"The list of proofreading marks on this page includes those illustrated on page 285 of the textbook and some additional editing marks that you may find on your papers...."

This is a pretty good resource. I've used these standard proofreading marks as a copywriter, when editing: and I still use them, now that I'm marking up my own work.

Exciting? Maybe not: but very, very useful.