<a href="http://securitytube.net/Defeating-SSL-using-SSLStrip-(Marlinspike-Blackhat)-video.aspx">http://securitytube.net/Defeating-SSL-using-SSLStrip-(Marlinspike-Blackhat)-video.aspx</a>
The way the SSLStrip tool works by:
Does an MITM on the HTTP connection
Replaces all the HTTPS links with HTTP ones but remembers the links which were changed
Communicates with the victim client on an HTTP connection for any secure link
Communicates with the legitimate server over HTTPS for the same secure link
Communication is transparently proxied between the victim client and the legitimate server
Images such as the favicon are replaced by images of the familiar "secure lock" icon, to build trust
As the MITM is taking places all passwords, credentials etc are stolen without the Client knowing