My vote goes to the Rio Carbon. 5GB CF card which will work fine (engineers have confirmed that Rio aren't bothering with making the CF card unusable in other devices - ie, it will work in both IDE and memory modes). Price is cheap too. Only problem is, that a memory card will NOT work in the Carbon (ie swapping in a replacement CF card) if it's not in IDE mode (the only ones that are in IDE mode are the "closed" cards, or the Seagate cards coming out next year which do both).
What you might want to consider, is the Archos Gmini220 which has a CF slot (you can use it like a filestore).
Yz