The Raspberry Pi has an on-board audio jack, which is super handy for all kinds of sound effects and speech, just plug and go! However, for when you want better audio for music playback, a USB audio card can greatly improve the sound quality and volume. That's because the on-board audio is generated by a PWM output and is minimally filtered. Don't get us wrong, it's a great thing to have audio on board but this USB audio card will make it even better.
We like this particular dongle for not being too bulky, you can plug it in without blocking the secondary USB port. It also works great, takes only a minute to configure and test it on your Pi.
At this time we have a tutorial for setting it up for audio output and line-level audio input.
This device also works great with Windows machines and should also function for Macs, but we are carrying it specifically for Pi usage.