Relay-like behavior without constant power
Digik-Key has lots of power latching relays. Go here and under Coil Type select single or dual coil, and Coil Voltage 5VDC.  Here's a dual coil one for about $4.  Note the hefty coil current though (150 ma), so you'll need to drive each coils with a transistor.

Although it will take two output pins (and two transistors), dual coil is probably a better way for you to go, since I assume the single coil ones work by operating the coil in one direction, and then reversing the current to disengage -- which would require an H-bridge.