The Penguin Book of English Folk Songs
Edited by Ralph Vaughan Williams and A.L. Lloyd. Originally published by Penguin Books in 1959, this little book became a hugely influential source of traditional English songs for a growing army of folk-singers in the 1960s and beyond. Out of print for many years, it was republished in by the English Folk Dance & Song Society, with the entirely appropriate new title Classic English Folk Songs.
The New Penguin Book of English Folk Songs, edited by Steve Roud and Julia Bishop, was published in 2012. This excellent volume - much more substantial than its forerunner - is a completely new work, containing a completely different selection of songs, not just a revised edition.