ADXL345 Triple Axis Accelerometer Arduino Library.
Tutorials: http://www.jarzebski.pl/arduino/czujniki-i-sensory/3-osiowy-akcelerometr-adxl345.html
YouTube: http://www.youtube.com/watch?v=90kI_tfOOzI
This library use I2C to communicate, 2 pins are required to interface