I'm sure that this $29 Mobile-USB-SD/MMC Hi-Fi Speaker won't produce perfect sound, but it gets points for looking 70s retro, being tiny, and playing music both from the computer, and almost every Flash memory-based media out there.

Add the remote control, and it looks like a nice solution for people in extremely small spaces, or perhaps for a bathroom.

Recharged/Powered by USB port
Built-in rechargeable Lithium-ion battery
4.5cm stereo speaker with 3W +3 W high quality sounds output
Support SDHC, SD, MMC and USB memory drive playback
Volume control switch
Play/Pause, Prev, Next control
Remote control with EQ selection
On/Off switch with LED power indicator
Standard 3.5mm aux-in audio plug apply with music player and digital products, e.g. PC, Mac, iPhone, iPod, PDA ... etc.
Compatible with any Windows and Macintosh platforms
Dimension: 107 x 110 x 113mm (approx.)
Weight: 376g

[USB Geek via Engadget]