Tangara is an open source, iPod-inspired portable music player
liliputing.com
liliputing.com
Also, the device might support SD cards up to 2TB, but browsing a huge music collection with only a clickwheel is painfully cumbersome. Even in the Rockbox-on-iPod days, I sometimes felt like I was scrolling down my Artists and Albums list more than actually listening to music.
The decent players like the Sansa Clip disappeared, and all the non-color-video-screen ones with long batteries are horrid cheap things that can't play songs in order, advertise ogg support but can't actually play it, can't handle random song metadata and silently drop such songs, bug out randomly, etc.
This looks cool despite the price... I don't commute or go out much any more so my uses are more limited, but I'm thinking of getting one anyway.