I share garbage cans with too many other apartments which means that the cans are often full when I take out the trash. My solution to this was to enter the garbage schedule into a raspberry pi, together with an estimated garbage can capacity in days. Now, differently colored LEDs light up on the Pi on days when there's probably still capacity left in the cans (i.e. the LED lights up the day after the garbage disposal and stays on for X days). I briefly considered the ethical implications of this (tragedy of the commons etc.) but when I realized that I produce so little garbage that I don't even use the trash cans every disposal cycle I concluded that what I'm doing here is probably fine. The code for this is a trivial ruby script:
https://github.com/RedNifre/pi_assistant_garbage/blob/master...I also added blue LEDs for a simplified weather forecast: A 12h clock face cut in 4 quarters, 1 LED per quarter, indicating rain. So if I leave the house in the morning I bring an umbrella if any of the next 12h LEDs is blue, but if I go to buy groceries I only check the current 3h block LED. I'm using openweathermap for this but I wouldn't recommend it, the forecasts are a lot worse than what I get from a simple weather forecast app on Android.
I also wrote a scraper for web comics that turns them into ebooks so I can read them on my ereader.
I'm currently thinking about automating my banking. I had a look at HBCI, but it's so terrible that I then considered website scraping. Then I heard that banks will be required to provide a sane API next year or so so I'm waiting for that first.