I used to write detailed lesson plans, now I have created a Keynote for each lesson that guides me and the students through what I need to cover, plus they can access it any time.
We also make extensive use of YouTube, with channels like Veritasium and Sixty Symbols explaining Physics in engaging ways.
I created a pretty elaborate multiple choice homework system that gives feedback and marks work. Building it in Google, with the data in Sheets, allows very powerful ways to collect and use the data using formulae and scripts. This lets us see who is falling behind, which questions are causing the most difficulties etc. Google sheets and the scripting is very, very powerful for a shared document system.
Similarly, I wrote a script that allows us to give individual, focused feedback to students after a written test identifying which topics and skills they struggled with. Again, in Sheets so this data links with everything else.
I now use my own app for keeping track of some assignments and class lists, but the key student data is available in a Google Sheet since it can pull in data from many locations (plus we can allow students to see their data from the sheet without duplication).
As a hobbyist programmer I tend to try things like iDoceo and Flubaroo, then take it my own direction. I’m happy to expand on what I do and how I made my choices if anyone’s interested.