Mr. Blond writes "Here is a description of how to build your own chat-cord for only 7 euro.
This is a solder free version of the hack shown in this earlier Slashdot article.
Now you can use any plain old phone to make calls over the internet, using Skype MSN-audio or any other VoIP software. Even the software from chatcord works fine with it, to make and accept calls using the buttons of your phone."