Overview of the book of Esther by pastor Chris Anderson - basically just a message I discovered while browsing on SermonAudio and enjoyed (I love sermonaduio... there's just so much there to explore.)
What I found helpful about this message is how Pastor Anderson sets the context historically of what's going on with Israel, and how Persia defeated Babylon and the Medes and Persians are in control at this point. Israel is in captivity to Persia, yet at the point of this book Israel is given the opportunity to return to their own land. Problem is, the land has been decimated and Jerusalem is in ruins. Another interesting detail is how Isaiah 45 prophecies about Cyrus, well in advance of the events of the book of Esther.
I thought this MP3 message, roughly a half hour, gave a solid overview of the background and message of the book of Esther.