The recording of the Revit 2013 API Webcast that Jeremy and I had presented is now available for download at the Webcast archive. The first half of the webcast is an introduction to Revit API and the second half covers the new API in Revit 2013. You can find this by looking for recordings under the "Revit API" category and with a date stamp of May 17, 2012. Here is the Jeremy's blog post with more details on this webcast recording.