Harvard University
Harvard Writing Center: Tips on Grammar, Punctuation and Style
Rather than lists of rules, this site provides practical advice on the use of commas, semicolons, dashes, hyphens, abbreviations, acronyms, split infinitives, "this," "that," italics, and underlining. CCSS.ELA-Literacy.CCRA.L.2
Khan Academy
Khan Academy: Italics, Underlines, and Quotes
Learn how to use italics, underlines, and quotes when writing titles of books, movies, songs, etc.