Links to many YAPC speaker slides are on the YAPC wiki.
And the hackathon begins...
I'm about to document the new dynamic_scope mechanism in a PDD. Meanwhile, Patrick Michaud, Will Coleda (coke) and Jerry Gay (particle) are here hacking on PGE, testing, and stuff.
In order to understand Parrot dynamic_scope, you should understand continuations. If you don't know about continuations, start by checking out the Wikipedia article on continuations and this introduction to continuations in Scheme. Extra credit for reading about Scheme's dymamic-wind.