The beautiful Welsh ballad, Lisa Lan, all done in D and C.
Ian B: for interesting new sounds, put your fingers in position for well known chords, then lift one finger off and see if you like the sound. For example, play a G chord and lift your finger off the highest string. The result is quite nice.
If anybody asks you what that intellectual new chord was, say something like "I believe it's an augmented 11th." That's what the rest of us do.