Hey Milo!
I use a Diamond Rio 500 wich comes with 64mb internal, plus mine has an extra 128mb, wich gives me enough space for songs.
I bought mine used WITH the card for $95 in the anandtech.com 'for sale/trade' forums.
Sound quality is incredibly good, and the unit itself is very small and light (only one AA battery)
The display is backlit and the menu system is powerful and comprehensive.
I think this model is not in production by the same name (Diamond changed their name to SonicBlue).
I recomend this little gadget its priceless for working out..
BUT..
IF you can afford it...
Get an Apple iPod.
AMAZING little player, 5gb in a small package, looks VERY stylish and sound quality is superb. THE best portable audio player ever made. Downside? goes for $500-