Here is a new entry, despite the name and purpose of this blog. My apologies.
The people at iRiver have lived up to their promise of supporting Ogg on the iMP250/350/450 players.
Download the public beta at iRiver
Check the results in the iMP-250 forum. There are restrictions on maximum and minimum bitrates of the files. In any case, it is good to see that firmware upgrading is actually used to provide new features for old(er) hardware.
Psst....people with a RioVolt 250 can turn their machine into an iMP-250 by flashing with a slightly modified image. Check the InterWeb.