These Cylinder Travel Speakers are a pretty nifty way to take a bit of stereo power with you wherever you go. Packed up, as a tube, they fit neatly into your bag and will even still work as speakers. Pull them apart and you can separate them from one another for a more pronounced stereo effect.
At a little over $30, they also aren't too hard on the wallet. They're encased in a matte black rubber body, run on four AAA batteries, and the 3.5 mm jack should fit pretty much everything out there (y'know, everything except the iPhone).