Apple provides an online serial number search to check a device's warranty coverage or AppleCare status. It gives the option to either set up a repair or contact Apple Support.
From the Apple home page, click on the Support tab, then select AppleCare from the second page of the gallery menu. On the AppleCare page, click on 'Check Coverage,' then enter your serial number into the bar and click continue. If your device is still eligible for Repairs and Service coverage or AppleCare, click on the Set Up a Repair button and click through the options to find out how to get your device fixed.