I bought an extra 64Mb piece of compact flash before going to Poland, figuring that in a month I'd take more than a hundred photos. I was right, but I'm not usually that long away from a computer... so, I had a look around for other purposes to which it could be put.
What I settled on was a Microboss MP3 Pocket, a cheap portable player with no frills but a good reputation from what few reviews I could find. Reviews in English, that is—Microboss is a German company, the only place I've ever seen their products being on eBay.
This isn't really a player suited to people who don't know a little about compact flash. It accepts only the thinner Type I cards, meaning it can hold up to 128Mb. It requires a card reader to get data onto the card; I have one because it's the easiest way to get photos from my camera. Finally, the Pocket chokes on some types of compact flash—it requires cards with a 4ms or less read time. One of the cards I have doesn't work with it, so that's the card which went back in my Canon Powershot. The other doesn't seem quite fast enough, as the first fraction of a second of each track gets 'eaten' during playback. Fortunately, there are quite simple workarounds for this (see below...)
On the plus side, sound quality is very decent; the earphones supplied were useless, replacement with ones capable of bass definitely being a worthwhile action. :D
Only having 64Mb to play with, I've settled on 80kbps mono 32kHz MP3s as a very listenable compromise, allowing me to pack over two hours onto the thing. Theoretically it can achieve 12 hours of playback from 2x AAA batteries, but as I have a boxful of Samsung Mercury-Cadmium types to use up, duration is currently a third of that.
The start glitches I solve by adding in an extra stage when I re-encode my MP3s to a lower bitrate (all batch processed, of course. Using free software called The GodFather, which is the be-all-and-end-all of audio file management.) I manually batch-file attach a second of silence encoded at the same MP3 bitrate to the start of each file, which works beautifully. The COPY command in DOS is still worth its weight in gold!