When to Use the Em Dash—and the En Dash and 3-Em Dash
by Sam Blum from Lifehacker on (#5HCTM)

If you want to master some of the more mysterious elements of grammar, we're going to have to talk about dashes-yes, those simple horizontal lines that seem to present themselves unannounced, only to stretch your prose further along the page. Did you know there are three-yes, three whole kinds of dashes-in the English...