Here's an index of some of Bill Monroe's songs:
http://www.bluegrasslyrics.com/monroe_index.cfm.htm
Of these you might want to hear the following:
Body and Soul
Close By
Down in the Willow Garden
First Whippoorwill
Kentucky Waltz
Memories of Mother and Dad
Mother's Only Sleeping
On the Old Kentucky Shore
Precious Memories
Sweetheart, You/ve Done me Wrong
Walls of Time
When the Golden Leaves Begin to Fall
(he has some great gospel stuff as well)
There are too many by Hank Williams to name. He is my all-time favorite.
From the Louvins, here's a discography:
http://www.bluegrasslyrics.com/louvin_index.cfm.htm
Try the following:
You're Running Wild
When I Stop Dreaming
The First One to Love You, the Last to Forget
If I Could Only Win Your Love
The Weapon of Prayer