I'm very big on portable electronics that recharge from a USB port. As swise mentioned, most business travelers these days travel with a laptop. I have one AC charger (an iGo Juice) for my laptop, and this also takes care of in-car and in-flight power, if needed. My Treo 650 smartphone has a retractable cable (third party, from Seido) that allows me to sync, charge, and use the phone as a data modem, all in one very small device. The Treo will play MP3s and audio books from either its internal memory or from an SD card of up to 1 GB capacity (I can also view a movie, stored on the SD card, on the Treo, but the display is so small that it's more of a novelty that truly useful), so I don't really need a separate music player. If I were to get one, I would be looking for one that charged and synced from the same USB cable. Once in a while, I do have an urge to listen to some music that I don't have on the Treo's SD card. I could get almost my entire CD collection on an iPod Mini. I bought a 20 GB iPod for my wife and ripped all of our CDs onto it for her, and it's only about 1/4 full.

Now, if I can just find a sync/charging cable for my Sony digital camera, so that I can leave that charger at home.