You can download my 2008 Pre-Purim Primer PDF by clicking here.
You can listen to a shiur by Mrs. Rena Spolter on the Hidden Character of Megillat Esther (in mp3 format) by clicking here. Source page download (pdf) is here.
You can listen to a shiur that I gave on "The True Nature of Purim" by clicking here.
If you want audio on the entire megillah, check out this link.