Rockbox has started releasing working builds for most recent iPod variants. Using it is more geek-friendly than user-friendly, but certainly functional, at least on my Nano.
The best part is that I can now use the same Ogg Vorbis encoded files on my PCs, empeg, and a Nano that I got as a gift.
It's not as slick as the empeg code, file-tree based organization rather than a database, and transfers are all done as a USB drive, for example.
Not a bad way to be portable until somebody releases a decent Sigmatel based player.
--Nathan