iriver - UMS Firmware. I got the iRiver iFP-799 thanks to Adam Curry. It has an impossibly hard user interface (that's another story), but the other pain is that it requires some wierdo software called the iRiver Music Manager (IMM) to upload.
iRiver is wonderful though. They have something called the USB Mass Storage Firmward that changes the player so that when you plug in the device, it just looks like a hard drive. Exactly what I need. But the pathetic thing is that this only works with iFP-500 or "Older":http://www.iriveramerica.com/support/ums.aspx players. Obviously, someone is worried about copyright protection or about making sure people use lousy iRiver software on their PCs.
The only small complexity is that for things that you record, you get it in .REC format, so you need some small utility call UMS Converter in order to turn these into MP3s. Actually, I think that this just renames .REC to .MP3, but I'll give it a try.
As for these players, they are butt ugly, but record directly into MP3 which is very convenient.
The other yuckie thing is that they prohibit copying an MP3 from your audio player up to a PC. Another yuck. Why do this?
There are other choices with direct MP3 encoding as "jetaudio.com":http://www.jetaudio.com/forums/showthread.php?t=3171 shows. Also there is a great forum at "MysticRiver.net":http://mysticriver.com that tells you what is up.