I recently resurrected my elderly (by gadget standards) Archos Jukebox 20 mp3 player. It's one of the earliest hard drive players, which I bought in 2002.
The interface on the device is terrible, most notably because it doesn't support playlists larger than 999 songs. This is silly considering that it holds 20 Gigs of music.
Well, today I discovered Rockbox, an open source firmware replacement for several players, including mine. Rockbox adds all sorts of features and, most importantly, raises the playlist limit to 20000--much more reasonable and, importantly, larger than the total number of songs I own.
Even cooler, Rockbox supports speaking menus, which means it says aloud the name of the current menu entry. With some effort, you can get it to speak filenames as well, which means you can navigate your playlists without looking. When I have the player in my pocket--or more importantly, in the car--that's going to come in real handy.
And Rockbox is open source. Unfortunately, that means I now have to resist the temptation to modify the firmware and write my own plugins for the thing.