First, the following is my FAVORITE video of Bob Dylan EVER. It's a clip from the movie The Other Side of the Mirror and he's singing Chimes of Freedom Flashing. It's an absolutely beautiful song and he's giddy through the whole thing, so he keeps laughing and smiling. It's very, very adorable. My favorite part starts at about seven minutes - if you're not up for watching a ten minute video, start there and you'll see the best of it.
Second. This is a video of George Harrison, my favorite Beatle, singing Here Comes the Sun with Paul Simon.
Third, here is George Harrison and Bob Dylan singing If Not For You.