This is a new resource that I just finished in July, 2008 that is designed to help understand how to use the Circle of Fifths to aid in playing by ear. This is demonstrated by drawing a circle on the circle to easily identify the major/minor diatonic chords in every key.
Hope this helpful!!
Here is picture taken at a Improvisation workshop I led in Seoul, Korea on January 14, 2008 at Church Music Explosion, 2008 which was sponsored by Sunmin Music.
Are you looking for some more in depth help in learning how to play by ear? ...If so, then check out the book, "The Secrets to Playing by Ear," by Jermaine Griggs at the link below.
GospelPianoToday.com is another incredible site if you are looking for great DVDs that teach practical improvisation for contemporary gospel styles of music. A good choice!