I build this speakers for my iPod a few years back, they are easy and cheap to make, I saw the original idea from a guy from Spain but he use a old VHS case, I had a DVD case laying around which makes them thinner and easy to carry around.
They are no Bose sound system, but they work and they're portable.
You need DVD case, a pair of Pc speakers (I added a couple of laptop speakers too) and a headphone cord with 1/8 plug for the input.
A solder gun, exact-o knife and electric tape, (or you can just tape it all together but it will be better to solder the wires)
Make a couple of holes to fit the speaker in place, I attached the speaker with a couple of small screws, but a hot glue gun will work too. For optional small set of speaker a the bottom (or top) I use the existing holes for the looking plastic thingy to hold the elements in place.
Inside just solder everything together to the wires and drive the 1/8 plug thru on of the holes out.,or make a little tread on one of the sides of the dvd case so you can put the wires in to make it easy to transport.