The host cache in Skype keeps a database of peers that Skype talked to upon last running. A host cache is one of several bootstrapping technologies that peer-to-peer networks use to connect a peer into the overlay network.
The host cache is kept in the shared.xml file located in the users home directory. If you look at how the host cache is stored, it looks like a jumble of hex.
A pattern does start to emerge and I wrote a tool to extract the IP address and port of each peer listed in the host cache. It is written in perl and requires the XML::Simple module. You can download the tool here.
I’ve only tested this with 2 different shared.xml files so let me know if you have any problems with it.