How do I play a sound with ardino and SD shield??

I'm simply trying to play a sound file (.wav and .mp3, that's not the problem though) loaded on an SD card and play it with a speaker (and amplifier). Can anyone give me some links to some tutorials/websites that explain how? I have tried to do it, but it just doesn't work and to be honest I'm not that familiar with SD cards and arduino. Please help.

Arduino Yun /Yun shield + USB sound adapter:

Play back mp3 file

Play back wav file

Repeat (Programming) Play MP3 Audio

Thanks sonnyyu, completely my fault I should of mentioned I was using UNO, so unfortunately it's not really much use.

Bump.........

You need mp3 shield:

SPARKFUN MP3 PLAYER SHIELD

$34.95

Yun Shield

$33.50

You have to tell us what sort of shield you have. A link to it would be good.

This part from adafruit can do just that for you, even without using Arduino:

Connect a button to one of its inputs and the corresponding file will play if you push the button. What fun?