Khan Academy 

Khan Academy has helped me throughout my academic career. I remember watching videos on dimensional analysis in chemistry classes and how it spoke to me when it came to crossing out the units that we did not need. Even before I went to bring up Khan Academy since I have not looked at it since when I was doing my pre-requisite classes for nursing school I remembered the black board with the colored writing on them and it was nice to see the same view again just now.   - Rachel Rytter 

https://www.khanacademy.org/math/algebra/x2f8bb11595b61c86:working-units/x2f8bb11595b61c86:rate-conversion/v/dimensional-analysis-units-algebraically

I found a video explaining this and it was nice to get a quick reminder on dimensional analysis. 

https://www.khanacademy.org/

I appreciate that this is a free resource. I think this is a great tool to bring learners to sometimes how things are worded in a book or class don't hit home and being able to watch a video and work a long with it can help.