I'm getting a sansa clip 8gb for $60 for working out. They are supposed to have great sound and good file support, and they are very small.
I use itunes on my mac, and was thinking about the ipod nano walmart has on sale for $48, but my concern as a musician is that the audio quality may suck from what I've read in reviews. I don't care about the random play or no video, I won't be looking at it while I work out, I just want to hear music I like at the gym. Oh, and while I would like the nano at $150, it's more than I need or want for this specific purpose.