I built an AirPi Wireless Speaker.  It consists of a raspberry pi, small amp circuit, powered usb hub, wifi adapter, bookshelf speaker, and a usb battery.  

You simply turn it on and wait for it to boot up then you can play music from your itunes or iphone using airplay.  I also have mpd and mpc installed so that androids can play music on it too.

It took about two weeks to complete and the instructions on how to install are posted below.

My reddit post

video of it working

video 2

How-To After the break.

These instructions are for a raspberry pi running debian, I used Occidentatlis 0.2 from adafruit.

sudo apt-get update

sudo apt-get upgrade

sudo amixer cset numid=3 1

sudo apt-get install git libao-dev libssl-dev libcrypt-openssl-rsa-perl libio-socket-inet6-perl libwww-perl avahi-utils libmodule-build-perl

git clone https://github.com/njh/perl-net-sdp.git perl-net-sdp

cd perl-net-sdp

perl Build.PL

sudo ./Build

sudo ./Build test

sudo ./Build install

cd ..

git clone https://github.com/hendrikw82/shairport.git

cd shairport

sudo make install

./shairport.pl -a AirPi (to test)

sudo cp shairport.init.sample /etc/init.d/shairport

sudo nano /etc/init.d/shairportchange

change it to look like this:

           DAEMON_ARGS-w $PIDFILE -a AirPi”

sudo chmod a+x shairport

sudo update-rc.d shairport defaults

sudo ./shairport start

Sources

Speaker 

Realistic Minimus 8ohm Ebay

speaker idea

initial airpi

second airpi

third airpi

monobox amp