Practical Typography
E-Books
One resource that I believe every designer should read and become familiar with is Butterrick’s Practical Typography. This is a well designed and clearly structured website which guides one through the fundamentals of typography. It covers everything from layout to the nitty-gritty of punctuation* use in a to-the-point, easy to follow format.
“Free Stuff” might be a little misleading for this one as Butterrick’s Practical Typography functions on a donation basis, and is definitely a resource worth paying for.
N.B. Butterick focuses only on American English punctuation.