My friend Marcus and I created an ear training video on identifying chords. It’s available at EarPractice, on Youtube, or by using the player below.

In the video I play a series of chords on the piano and after each one, pause for the viewer to identify the kind of chord (such as Major, minor, dominant-seventh) and the key (such as C, A, etc), before revealing the answer. This is a useful exercise and is something you can do with a friend too, once you get the idea.