The best first place to start is the Fasola website. There you can find information about the singing, the books, where to find other singers, and nearly anything else you might want to know.
You can buy your own copy of the Sacred Harp at a singing or directly from the source, the Sacred Harp Publishing Company. If you buy it anywhere else, you'll probably pay too much.
And if you can, go to Camp Fasola. What a wonderful experience that is!
If you want to listen to separate parts of songs (or hear the songs without the words), check out these MIDI files of all the songs in several shapenote hymnals. To listen to these files, you will need to download a FREE plugin (just read and follow the directions on the site). You can also download the whole program, which will cost you $20, but it is not required. Terre Schill and all her supporters deserve great thanks for all the work that has gone into these files!
The Pilgrim Production website offers many live recordings from all-day singings (and includes song lists so you can sing along).
Or you can watch YouTube videos from Sacred Harp singings.
Be sure to catch this Emmy-winning documentary filmed in Hoboken, GA. (Note, it is in two parts, 10 minutes, total.)
Prairie Harmony singers from Fairfield, IA, have recorded some of their favorite shapenote songs, available at www.fairfolk.org/prairieharmony. They write "We intentionally recorded the 'voice' of the space we were in, the barrel vaulted 1855 Presbyterian Church in Bentonsport, Iowa, a space designed for singing. The recording is live, unedited and sung with the feeling and joy that we feel when we sing together as we have over the past 15 years. The singers are all from the Southeast Iowa area and the songs are samples from the sacred harp tradition spanning the 18th through the 20th centuries."
And also check out Dust-to-Digital, a great musical resource which combines rare, essential recordings with historic images and detailed texts describing the artists and their works. Their 2004 release "Goodbye, Babylon", which includes Sacred Harp singing, was nominated for a Grammy and won an Alex Award. In 2009, founder Lance Ledbetter was named one of "50 Visionaries Who Are Changing Your World" by Utne Reader!
A great article from Paste Magazine about Sacred Harp Singing in Alabama (and elsewhere).
But if you're one of those people who've been convinced they can not (or should not) sing, then you need to read this
essay by Martha Henderson, a singer from the Twin Cities.
When choosing a song to lead (especially if you're a new singer), it's often helpful to pick something that other singers know. Here's a list of the songs led at all-day singings in 2004, sorted by frequency (songs at the top were led more often than songs at the bottom).
Here's a list entitled "Familiar Songs" which originated in Boulder. If you're looking for a song to lead, anything from this list would be a good start!
And if you're thinking about songs you'd like led when you're no longer around to lead them, add your name and directives to the PartingHand wiki.