I've been working on a project for a few weeks now, so it's time to introduce it !
My project is a LCD dash for Honda cars. it connects to the car's Engine Control Unit and fetches data to display it on a KS0108 based LCD.
I've chosen to use the Mega to achieve this because of its multiple hardware serial ports. The arduino connects to the ECU via a ttl serial connection, so I could have used the regular arduino but I wanted to keep the USB serial port for monitoring or future features.
you may check the project's page: http://code.google.com/p/rzdash/ there is a video link on the main page.
the code still needs a lot of improvement but is working fine.