Dr. Kenneth Cole, Director of Training in Psychology at the VA in Long Beach, gives a nice interview on ACT as part of a podcast.  The interview is in two parts.

He provides an overview of where ACT has come from in terms of its history. He also differentiates it in some ways from more traditional CBT. He also refers to the hexaflex , the slang term for the ACT hexagon model, and provides an overview of at least some of the model. He discusses a bit about ACT for anxiety disorders. It's a really solid job in a brief amount of time and serves as a pretty good brief intro for those new to the therapy.  Fun to listen to.

See the links below for the two interviews:

Part 1

Part 2