I bought a Sony portable speaker system for my honeymoon in Europe last fall and was mightily impressed. I had it hooked up to my Ipaq and used the PC Card expansion pack with a 2GB PC card to carry most of our CD collection around Italy with us. Great in hotel rooms etc. I'll be taking it on a two day car trip next week, loaded up with This American Life episodes (NPR) in Real Audio as well as WMA files from my CD collection.
The SRS-T77 is the size of two CDs stacked, has a world AC adapter as well as taking AA batteries (great bonus), and the sound is really quite good indeed. In fact I've found that since the audio output of the Ipaq is at such a high level, you can actually use these with no power amplification at all. The volume isn't as high, but it's definitely listenable!
http://www.sonystyle.com/home/item.j...id=8902&type=o