This morning I upgraded to Thunderbird 3.0 from 2.0 on Windows and realized I have no idea what my "Master Password" is set to in Thunderbird.  Luckily, I found this web page that explains how to reset the master passsord, which also dumps everything stored in it.

Tools --> Error Console

Type the following command in the window and press "Evaluate"

    openDialog('chrome://pippki/content/resetpassword.xul')

--Chris