After seeing one of those extremely inexpensive Android tablets at a PC store, Arduino forum member carl47 decided that it would make a great way to add a large, colourful display to his Arduino. The process of connection and display uses various forms of code, including firmata on the Arduino and of course a custom Android app, however the author does offer all the downloads required to make it work. You'll need Android SDK v3.1 or greater to get the app for your tablet going, however the results will be worth it, for example:
Then with a little work your Arduino can have a fantastic and portable output device. For more information and relevant links, check out the Arduino forum. And for more, we're on twitter and Google+, so follow us for news and product updates as well.
If you're looking for an Arduino-compatible board for Android work with an inbuilt USB host shield, look no further as we have the Freetronics USBDroid board:
Apart from being a fully Arduino Uno-compatible, it has onboard microSD socket and the full USB socket and host-mode controller. As well as the Bluetooth application described above, this is the ideal platform for developing peripherals or projects based around Android devices with ADK (Android Developer Kit) functionality, but without requiring a USB host controller shield stacked onto an Arduino. For more information and to order, visit the product page here.