A pretty comprehensive pile of links is available at contradancelinks.com. If this interests you, there goes your Sunday! I apologize in advance for the many dead links you're likely to encounter. The grassroots/volunteer nature of the contradance community tends to mean that things come and go, but there's always someone keeping their corner of it alive.
Dance manuals from the Library of Congress. Contra grew up alongside of (and had some pretty complex interactions with) formal European-style dance traditions taught by dancing-masters in the 18th and 19th centuries. Early American dance manuals often combine a bit from both traditions.