Songs for a 30-something's IPOD

I have a friend who will be turning 30 next month.
I happened to hear some of the songs she has on her ipod.
John Denver.
The Mamas and Papas.
Cat Stevens.

I linked a few others that she might like from my era:

This Peter, Paul and Mary song is one I listened to all the time as a kid.

Jim Croce was another one of my favorites from the 70's. He died too soon.

This Harry Chapin song is another classic tune. He died too soon.

Nobody compares to Janis Joplin. She died too soon. I'm still not over it.

While my friend preferred California Dreaming, this is my favorite Mamas and Papas tune.