I was inspired by fungus amungus's Munny Speaker instructable but thought that if it was to have a good sound then it would need amplifying. I bought a very cheap set of iPod/laptop speakers to supply the actual speakers and the amp.
This project could work great with a second hand pair of computer speakers.
You will need:
Munny Dolls. (x2).
iPod speakers
Pliers
Soldering Iron
Craft Knife
Philipshead screwdriver
Hacksaw
Insulated wire
Scissors
Hot Glue gun
Vacuum Former (ok, so you prob dont have one but you will need a case for the amp)

Step 1: Breaking Things

The first step is to break apart the speakers. You need to careful extract the speaker cones being careful not to damage them.
The Amp circuit board should also be taken out if you are going to make another case to house it. If you can/want to use the existing box, then leave it all connected. In hindsight, I probably should have done that rather than go to all the effort of making a new case.

Step 2: Amp Circut

Remove the amp circuit and speaker cones. With Care!

Step 3: Template for Speaker

Trace around the speaker cone onto a piece of paper and cut out the centre.

Step 4: Trace Template

Trace around the template on to the Munny Doll's 'face'.

Step 5: Cut Hole for the Speaker.

CAREFULLY cut out the hole. It is very easy to push too hard and to over-cut.
Repeat for both dolls.
Test for fit and trim as needed.

Step 6: Install Speakers.

Drill a hole in the base of the Munny Doll
Bring the insulated wire up through this hole, through the neck and out the 'face'.
Solder wires onto the speaker.
Stuff cotton wool into the head cavity for sound dampening.
CAREFULLY glue the speakers in place and leave to dry.

Step 7: Make Base

I wanted to not use the bright orange case so I decided to create my own.
There are Instructables on how to make your own vacuum former and I reckon they are a great addition to any workshop.
Larger Munny dolls could maybe house a battery pack and the amp circuit. Depends on the circuit.

Step 8: Assemble Base.

Drill holes in you base that align with the volume buttons, headphone jack and the on/off switch. I recommend that they are a made a little bigger that you think to allow for wiggle room when assembling.
Here I have installed the circuit and the battery pack.

Step 9: "Weather With You" by Crowded House

The Munnys now live on my desktop with the amp case trimmed down and hiding behind the computer.
If I was to make them again, I would use the large Munny Dolls and hide all the electronics inside the body cavity of the dolls. You could have volume and power switches mounted on their backs.