While I have done similar projects to this one, on a more limited scale, it's nice to see HiSET do some of the heavy lifting. Below you will find a new resource from HiSET copied from their website.
Academy Math Videos
In collaboration with Khan Academy, the HiSET® program has
identified videos and exercises that can assist you in preparing for the HiSET
Math test. These training videos can improve the fundamental skills in Numbers
and Operations, Geometry, Data Analysis and Algebra that you need to be
successful on the HiSET Math test. See the Khan
Academy Instructional Support Videos and Exercises (PDF) for more