SONICblue's Rio Riot looks pretty nice. I saw this a week or two ago but didn't care to post about it because at the time they didn't have physical dimension information on the site. 5 3/8" x 3 5/8" x 1 3/8" and 10 oz. (including the battery!). Not bad. Stores 20 GB of MP3/WMA audio. And runs for 10 hours. And it includes a FM tuner. $399.95 MSRP.
It also has a feature called the Rio DJ that basically remembers the songs that you play most often and can create playlists by mixing your favorite songs. Frankly, I'd like something like that for Winamp.
There are just a couple of things that would make this thing perfect. Sure, it could always be smaller and cheaper, but I wish it would allow itself to be used as a generic storage device. I have a lot of music, but not quite 20 GB worth yet. That extra space would be nice for shuttling files to and from the office. And it supports USB, but not USB 2.0. Why didn't they check with me first?