I put a Raspberry Pi into a radio from the 80's to get a portable AirPlay device
jeena.net
jeena.net
Some photos on FB: https://facebook.com/hervalfreire/albums/10152327503600754/?... (planned on doing a blog post but got sidetracked building other things)
I've just set mine up for timelapses at the moment. Nothing fancy, but it does make for pretty videos every day :) https://www.youtube.com/watch?v=rVxBJN5Pd_E (since this one, have worked out how to turn the LED off, and I don't take it through the night any more).
Good times, love the pi.
Basic instructions here: http://wiki.psdavey.com/my-setup-for-timelapse.html
It has enough space to put in a pi,dac,amp into the middle box in the second picture (which is perfectly centred) then I'm going to build some mdf cabinets and put the speakers either side (with lots of dampening).
Going to keep (and make work) all the front switches, power output (top right rectangle) is going to be replaced with a backlit LCD display and the tuning dial (main face) is going to be kept but backlit with LED's that change color to indicate station/volume.
On the back, audio output (in case I want to use external speakers) plus HDMI and USB connections (so I can plug a monitor and keyboard in to do config without disassembly).
Case had so much internal space I was tempted to put a media PC in it but I have one already and a radio seems fitting somehow.
However if all you want is a working device, here's one for $60: http://www.amazon.com/iHome-AirPlay-Rechargeable-Wireless-Sy... And there are much cheaper choices if you stick to bluetooth.
For hacking things together, there is a $30 dongle that takes power and delivers 3.5mm audio: http://www.amazon.com/Sabrent-Receiver-Supports-Portable-WF-...
There is a critical mass issue with things like this in needing to have several of the microcontroller devices available, so you don't feel bad about "burning" on by actually embedding it in a project.
If so, we (SpeakerBlast.com) might be able to help.