<p>If you are taking undergraduate math and science courses this site looks really good.</p>
<p><a href="https://www.clutchprep.com/">https://www.clutchprep.com/</a></p>
<p>It has 100s of hours of video lectures, notes, and other study resources for the typical textbooks used in undergraduate level calculus, physics, chemistry, statistics, and biology courses. Best part is that its free. The videos and notes are tailored specifically to the book that you select.</p>