Here are some of the websites that were most helpful to my study, in no particular order.
Cybrary is an incredibly helpful website with lots of free training (and paid training, including labs). The CISSP review by Kelly is outstanding and really helped me cement important topics. It’s just a bird’s-eye view and doesn’t replace thorough study of the material, but is excellent review before taking the exam.
The Sunflower Study Guide is a valuable resource to make sure you have all your bases covered. Literally every single base. It’s 42 pages of tiny print, and everything in it is useful. There is a lot of good advice and useful information at the same website. Explore.