Any music player for gym must be flash-based, not containing a miniature hard drive. They're smaller and lighter, and more resistant to breaking when dropped. There are in fact iPod models that fit this description.

I'm happy with my iAudio 7. It is small and light, holds jiggerbytes of music, plays all kinds of formats like .ogg and .flac, and you can put music (or any other file really) onto or off it just by plugging into into a computer via a USB cable, then dragging and dropping files. You know, like a sane and functional piece of kit, not that weird and broken iTunes thing.