With Simplytest.me there is no need to install an entire site just to test out a module. You can quickly and easily spin up a site with your desired module, theme or distribution and play around without any overhead.
I got back into Drupal about a year before Drupal 7 was released, so I built a couple of sites in Drupal 6. Then in January I completely switched over to D7 when it was released. Because I decided to make the switch right away, I was running into a lot of bugs/issues that hadn't been resolved yet. So, I started to make videos helping other people with the problems I found.
With the videos I made, I realized that I had shown some solutions, but people still had a lot of questions about edge cases. That was when I saw the light, and had the idea to put together series of short videos covering different topics. This format allowed me go in-depth with each module. I'm glad to be sharing these videos on OSTraining!