Anyway, here are the DefCon slides: https://community.rapid7.com/docs/DOC-1504
And here is the long awaited Whitepaper on testing web services: https://community.rapid7.com/docs/DOC-1505
The Web Application Hackers Handbook is supposed to be updated to cover web services... I should have my copy by the end of the week... Would be nice to have now, as I'm in the middle of a pen test that's employing JSON.
Anyway... happy reading!