One of my cousins actually edited the OSH - Hugh McGraw out in Bremen GA.
There is an absolutely wonderful DVD out on the history and practice of the Sacred Harp - they even have a website.
Awake My Soul: The Story of the Sacred Harp
Lots of fun stuff on the website, including lots of audio tracks and a trailer for the movie. The primary singers for the movie are a bit more polished than your average SH singers, but they are an actual SH group and they've retained the vigor and force of the old style singers.
I love one comment in the film -- one of the guys they interviewed said somebody asked him, "Do you want to sound like a bunch of uneducated Southerners?" and he said, "Well . . . YEAH!"
Sometimes SH singing is called "Fa-So-La Singing".
And it is really an education to try to sing the NAMES of the notes instead of the WORDS! You have to shift gears inside your head. I'm still not very good at it!