[brrritish!]

http://www.bored.com/musictests/

Click on a link in the top left for the three different tests, the pitch is the best imo. I would like to see someone differ two pitches 0.125Hz apart

 

[vagarach]

I could tell tones up to 0.75Hz apart, it didn't get any closer for me though! I was using the laptop speakers so it may have been harder to tell at that range.

 

[Assorted]

I believe the quote "excellent musicians rarely get above 80%" is quite inaccurate :/

 

[LawnGnome]

ouch, only got about 20hz separation. Guess that isn't bad for someone who was literally deaf as a infant and had to undergo many in ear operations.