Neil Young has several. Laughing Lady. My favorite is harvest Moon.
Here's a nice tutorial from Guitar Noise on how to play it.
BTW, some other nice songs to learn there.
Steve Earl also has several.
As for dropped D, I like to put a capo on the second fret, from above, and not capo the sixth string. That effectively gives you a dropped D (in the key of E), but has the added advantage of allowing you to play a G or other chords, and fret the sixth string. I play Norwegian Wood this way. Most any song you play in D (which would make it in E) can easily be used this way.