John Strand of Pauldotcom allowed me to post this video that shows how to use SSLStrip to proxy an SSL connection and sniff it, without those annoying warning messages about the cert that other tools give. From John's description:
With SSLStrip we have the ability to strip SSL from a sessions. Using this tool we have the capability to capture in clear text user IDs and passwords.
 

SSLStrip from John Strand on Vimeo.