Music
Music is pretty much an essential element of the human existence.
Install RockBox on your music player. RockBox is firmware for music players. That means it's the brains for your "mp3 player" or "ipod". After installing RockBox, you'll want to call it a music / media player because your device will support much more than the mp3 format.
There are many brands that support the free ogg file format straight from the factory.
But the RockBox software is even cooler. It is completely configurable to do what you want it to do. It will even talk to you so that you can hear the menu instead of squinting at the tiny screen in broad daylight while driving in traffic (not that anybody ever does that).
The only "problem" is that not all players support ogg, and RockBox is not developed to support all players.