The Kensington FX 300 Speaker to Go combines a flimsy speaker and an even more flimsy traveling case to great effect. It's one of those, "Wow, I can take this anywhere!" kind of devices that really have limited use. Users stuff their MP3 player into the appropriate spot inside the case which in turn activates the speaker. Yes, it's all very high-tech. The case even has storage compartments for all your credit cards and Cialis!
The volume adjustment knob is on the outside and the batteries last 10 hours. It'll retail for $30 when it comes out in the near future.