Largest site of folk music and folk songs, divided by nationality, is ingeb.org, with many links and an active forum.
The specialty there is German folk music, Deutsche Leider (the Leader in Lieder mit Midi Melodies!) [Deutsche Volkslieder]
[Kinderlieder, Children’s Songs]
There’s also a Yahoo Group for German Music that has MIDI(!) samples of various folk classics like “Lili Marleen.” For MP3s, go to Deutschland Spot.
Along with songs by various nationalities and ethnic music, ingeb.org has Songs of the Sea with many old seafaring songs and nautical themed music, including “Cape Cod Girls.”