I built these a while ago out of some laptop speakers, but today I gave them a new and improved look. There is no amplifier; they are only powered by the headphone jack. I have tested them against the ipod touch 2g's built in speaker, and they are a good bit louder, not to mention they sound better.
They are made out of aluminum flashing, the end of an 1/8" stereo cable, hot glue, wire screen, JB weld, and lots of hard labor
Here's a picture of them originally:
Now:
for an idea of thickness:
I made a video of them playing to give some idea of volume and quality. They sound pretty terrible in the video, because my camera is a piece of crap, but in real life they are a little better. I think it is pretty obvious from their size that they are a bit lacking when it comes to bass though.
video:
I can post instructions if anyone wants to build their own, not that they are very difficult to make.