Okay, here is an update. This answer requires permission and may be considered hacking. It also may violate wiretapping laws. REALLY REALLY REALLY make sure it is legal and you have permission!!!!!!!
But if you are doing research or testing, you could probably use something like Paros. Paros is a security tool for web application vulnerability assessment. This is a man in the middle type of situation. The skype ssl's to the proxy, and the proxy ssl's onto the destination. The proxy sees everything that goes through.
Please do not use this covertly or illegality.
Fred