Logic Level Converter Bi-Directional
The SparkFun bi-directional logic level converter is a small device that safely steps down 5V signals to 3.3V and steps up 3.3V to 5V at the same time. The converter works also with other voltages. This converter can pass data from high to low and/or low to high on all channels. It can be used with normal serial, I2C, SPI and any other digital signal.
More information is available on the website of Sparkfun.