Watch the Week 5: Ear Training - Chords on the Fly online guitar lesson by Roberto Dalla Vecchia from Flat Out Flatpicking
Choose a key first, then using the chord chart (see attached PDF file), play a very famous song on the fly at a slow tempo. Try your best not to make too many mistakes. Choose a different song every day and test your ability to play what you hear in your head.
Simple songs are: "La Bamba", "Obladi Oblada", "Bye Bye Love", "Teach Your Children", "Me and Bobby McGee", "Folsom Prison Blues", "Let It Be", "With Or Without You", "Summertime Blues", "Helpless", "Johnny B. Goode"
To take this a step further, play the same songs in all 5 keys.