Build Your Own Giant 555. This is definitely not practical, but it is fun. It’s educational, too!
BeagleBone: 9 Add-Ons That Power It Past Raspberry Pi. I have a BeagleBone, and while I haven’t played around with it a lot yet, I am liking it. I think it’s a better choice for amateur radio apps than the Raspberry Pi.
How to Use a Digital Oscilloscope. Now that scopes are so cheap, more and more hams have them. They do work differently than analog scopes, and this course will help you use yours better, if you have one.