You might have to scroll the page a little to see all of this piano chord finder. I was torn between having a nice large interface you can read easily or or having it all compact so that it fits on the screen. Depending on your browser, the bottom part my be cut off, but I tried to put the most common buttons towards the top.

If you roll over a piano key, once a chord is selected, a box will appear that gives relevant information about how that piano key relates to the chord.