I find that the Khan Academy website and program in general is extremely helpful for students to see where they may be struggling.
Community Review for Khan Academy
My Take
I find this website to be extremely useful for educators of any kind. Khan Academy offers tools to help students with a very broad range of topics. There are even prep courses that people can buy for the ACT, SAT, and even the MCAT. When a student gets a question wrong, it explains why it is wrong, and also says why the other answers are incorrect. There are also quizzes at the end of each chapter that is generated in order to have the students assess themselves over the material they have been working on. It is extremely helpful for preparation for exams for any grade level. Undergraduate student or not, there is a subject that is given for all levels of education.
How I Use It
I would use this resource in my teaching by assigning work to my students to complete each week about what we learned about in the past week. It is a very good website to keep the mind refreshed with necessary material.