Since we have many new members (and several people lately have been asking me what good HA can do), we should start a thread which shows what we are doing with our home automation, and why! You don't have to list everything (such as the very basic lighting control), but try to focus on things which are more unique/useful). For the obvious reasons, don't reveal too many details about your security setup 

- Medication reminder: the system will remind me when the next medication has to be taken. It is set to remind me every 5 hours, and only remind me if there is motion once past the minimum 5 hours (in case I fell asleep or I am not home). It will keep reminding me every 15 minutes until I reset the timer. I use a big red button remote (KR15A), hit it once to announce how much time remaining until next dose, hit it again within 5 seconds to reset the timer. Works great!
- Monitor garage door status: issue reminders every 15 minutes when the door is open, send out an email when the door has been open for more than 15 minutes AND the car is not in the garage.
- Monitor Freezer doors: announce when a door has been open for longer than 60 seconds, using DS10A wireless door/window sensors (still being tuned).
- IR control: mute all audio equipment and TV's when the phone rings, so the Caller-ID announcement can be heard. Turn on PiP/Twin View when there is motion outside, or the garage door opens, showing a live camera feed. Also mute all audio systems if there is a high priority announcement (such as as the medication reminder), unmute once the announcement has been made.
- Monitor Water Softener: I tend to forget to refill the tank with salt, so this system will remind me that I am almost out, and need to purchase more. It eventually will become part of the 'shopping list generator' project.
- Monitor washer & dryer: Since the appliances are in the basement, it is hard to hear the buzzer. So the system will announce when the washer/dryer starts (sometimes, I forget to turn the dryer on after switching a load), and when they are done. Very WAF friendly! Check this how-to if you are interested in learning more about this setup.
- Kitchen cabinet lights: Turn on the kitchen cabinet lights whenever someone is in the kitchen. I use a combination of pressure sensors and motion sensors, works pretty well.
- Car starter: I built a cradle for my remote keyfob, so my system can control the remote starter by activating a solenoid. My system will start the car every morning after I wake up (using time restrictions and motion detectors), so it is all nice and warm when I am ready to leave for work. I am planning on adding the outside temperature as a condition so it can decide if it should start the car a few minutes before I leave (summer) or if it should start it 15-20 minutes in advance (winter).
- System announcements: Medication reminder, CNN breaking news, weather alerts, amber alert, caller ID, appliance status, garage door status, event reminders, good morning function, good night function, mouse activity and trap activation, driveway motion detected, etc.
- Closet lighting: Automatically turn on the lights on/off whenever entering a walk-in closet, using DS10A door/window sensors.
- Car status: Using a motion sensor in my car, the house will know when the car is parked in the garage or when I am on the road. This allows the system to trigger certain events when I arrive home, including announcing "honey, I'm home" to make sure I don't scare the wife when I arrive home from work a little earlier than expected. I am going to switch to the palm pad based system soon (details posted in BSR's latest how-to).
- Garage door control: Using my Ocelot and a SECU-16 module, I can control my garage door, allowing me to open it remotely (i.e. web, cell phone, etc.), or close it automatically if it is after midnight and I forgot to close it (and somehow missed the security announcements).
- Battery recharger: My system monitors how much time I spend in my shop, and based on that starts a recharging cycle for my all my battery powered equipment once I leave the area.