I have had the pleasure of presenting a project at Maker Faire NY in 2011. I created a home security system with a covert notification to the user about intruders ("Notify Me Now"). You can see the code I wrote and learn more about my project by clicking here.
The new code can be downloaded here [edit: outdated!]
The current release can be downloaded here:
More recently I have been working on an automatic dog food dispenser.
This is the original prototype that I built. I built a new version out of plastic. The new version has WiFi instead of Ethernet, and can automatically feed an animal from a PC or a mac. The feeder has an Arduino Ethernet at the core, attached to a servo. The Ethernet cord connects to the wireless router inside of the assembly. Although it has a few leaks, it still works great!
By running a program on windows or mac, it will open the feeder's site and feed. This can be automated using task scheduler or iCalender.
The new code code can be downloaded here: