I'm sure some won't like it, but I think a combination of AirPlay (an Apple protocol for streaming audio via WiFi from iTunes and any of their devices to compatible speakers, Apple TVs or their WiFi router, the Airport Express. The Airport Express has a 3.5mm output and a USB port for plugging your printer into it and printing from anywhere. It's handy if you frequently travel and you only have an Ethernet connection.
http://www.apple.com/itunes/airplay/
Airport Express
Expensive box that happens to support AirPlayThe other way is to use Bluetooth, but the range is very bad. If you are using this in a single room it will be OK, otherwise, you will need to use something to extend its range or use other technology to get the audio to the other room (just don't run an audio cable without any shilding through the same tube your mains wiring is

). I have been looking for a Bluetooth to 3.5mm adapter since I got my first Bluetooth device. I finally found it:
A lovely Belkin F8Z492-P.
I have been looking for this for years.Now you just have to get some of these for your speakers and a set of bluetooth headphones. I don't like the ones that hang behind your neck, but hey are the most popular. Getting ones with microphone can be handy too. Here's something ironic:
http://www.amazon.com/Sony-Ericsson-Bluetooth-Stereo-Headset/dp/B003DQ1DCM/ref=sr_1_10?s=electronics&ie=UTF8&qid=1328141323&sr=1-10It comes with a 3.5mm output as well, so you can use it as an adapter like the ones above and as an FM radio.
That's for wireless solutions. I will come up with wired solutions later because my mind and I are tired. You can put the switch on the post above in a nice box. I have one and I have thought of doing it, but the shaft is too long and I have to put more stuff in the box so it is useful and heavy enough. I am thinking about adding an FM receiver or maybe repurposing an old CD-ROM with an ATAPI interface into a remote controlled CD-player (oh wait, I have no CDs because I'm a 21st century "kiddie").
Edit: perhaps I could add an equalizer and a loudness switch to the audio switch.