From Quora: My Answer to "Where can I find more writing and language questions to prepare for the SAT if I've done all the Khan Academy questions?"

You can buy (bookstore or online) or borrow (from a library, I suppose) any SAT practice exam book - e.g., Barron’s SAT, tons of books by Kaplan, Princeton Review, or Gruber. You can also just Google “free SAT practice exam” to find other test prep or tutoring companies’ sample tests or problems.