There's a letter from Skip James to Tom Jacobson up for auction on eBay. If you have 5K lying around it could be yours. Includes hand-written lyrics for Devil Got My Woman. The eBay listing includes scans of the letter, so worth looking at even if you ain't likely to bid...
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=300292038825
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=300292038825