Here's a test to see how good an ear you have. It seemed to help if I closed my eyes. I scored in the normal range. http://jakemandell.com/tonedeaf/ (Mods, if this is too far off topic, please move. I thought more people would see it here.)
Edited to add: On a web page leading up to the test, the creator of the test said that he made it so tough a pro musician could score 80%.
Edited to add: On a web page leading up to the test, the creator of the test said that he made it so tough a pro musician could score 80%.