Arduino is the name of a computer hardware and software manufacturer, as well as a user community that designs and manufactures kits for building interactive objects that can sense and interact with the physical world. The company mainly produces under-sized and inexpensive single-board computers, perfect for hobbyist projects where a small, programmable computer is required. They utilize either 8-bit or 32-bit processors and use flash memory and EEPROM for program and data storage.
Arduino computing hardware (such as the Duemilanove show above) has been used in many projects. For example, they have been attached to a balloon to take photographs of our planet from high altitudes and then transmit those images back to Earth over a wireless or satellite connection. The company website is located at www.arduino.cc.