Resources: (Minnow here!)
These are on Bluebook (downloadable program) with full practice tests. These are timed and a perfect way to prepare for the exam. Although some of these tests are easier than the actual version, it is still an opportunity to learn the test question structures and get a feel of the real exam. Also free!
This is a pretty general source. It is a perfect base to review the content of the topics that will be present during the exam. With the new digital adaptation, I hope Khan Academy will continue to update its resources. It's also free!
This website primarily focuses upon AP courses, but there are SAT practice questions and tests located on the bottom left. The practice questions will split them into 10 so it is a good way of studying and timing yourself for each chunk. It is also free!! (Additionally, there are full tests too)
This has some free resources but their textbooks are phenomenal for understanding the test. It is almost a better version of Khan Academy but the textbooks do cost money.