I bought some AXICOM latching relays on Ebay for cheap.  They are 3V relays.  Latching relays are nice because there is no holding current required to keep in one state or the other.  All you have to do is drive them differentially and pulse them +/- to put it in one state and then pulse it -/+ to put it in the other state.

To use these with an Arduino Uno whose outputs I/O are 5 volt, level translation is required.  There are chips that do level translation but when I wanted to set one of these up, I did not have any level-translator ICs in my lab.  I have plenty of bipolar transistors, however.  Using 2n3904 and 2n3906 transistors, I constructed this simple circuit.  I derive the 3.3V power from the Arduino Uno board.