Skype 3.0.0.190 is now in general release for Windows, amongst all the changes mentioned in the Skype Garage post is this little gem:

change: API: application can connect to oneself

This adresses an interesting issue. Unlike most network addressing schemes, skype connects to a username, and there is nothing to stop a user running skype on many machines as the same user. When app2app messaging connects to a user, you get an array of streams that connect you to all the endpoints for that user.

However, in the past you could not make a connection to yourself, and now you can. So if you connect to your own username you will get back an array of streams to your other instances. This could become quite useful for keeping all kinds of things synchronized across multiple machines.