I would have to say that data collection is one of my hobbies. I have collected hundreds of research files in PDF format over the course of many years. In fact, this collection is still going on to this very day. One can learn new things when they take up new hobbies or sports.
Here is a PDF I had written up on individual hobbies and sports. I will provide a link to the pdf via my Google drive and my Amazon drive. You can choose which platform you'd like to download the pdf via.