There's a PDF book on this:
http://www.pragprog.com/titles/jfpaypal/payment-processing-with-paypal-and-ruby
-FDj (No affiliation with PragProg or the author)
There's a PDF book on this:
http://www.pragprog.com/titles/jfpaypal/payment-processing-with-paypal-and-ruby
-FDj (No affiliation with PragProg or the author)