If you don't have fancy wireless speakers, but want you play your music through your whole house, you can connect a car FM transmitter to the line out of your audio system and pick it up on radios all though the house and garden :)
I'm some cases you might need to add an old cassette deck between the stereo and the transmitter so you can control the volume levels.
Edit : someone asked for more details.
Most of the transmitters work on 12 volts, so you might have to butcher an old 12V dc power supply from a rechargeable torch, dead scanner, old phone charger to run it. I've soldered mine to a cigarette lighter socket.
It's hard to give specific instructions because everyone's stereo is different. Mine is being fed from a pc connected to an equaliser connected with a double rca adapter connected to a tape deck and amplifier. The tape deck, left on record mode, functions as a simple pre-amplifier which lets me see how much signal I'm sending out - too high and the music distorts.
