Shtoom is a open-source, cross-platform VoIP softphone, implemented in Python. As well as the basic phone, the package also includes a number of other applications -

• shtoom - the end-user phone
• shtam - a simple answering machine/voicemail application
• shmessage - an announcement server

Shtoom should work on Windows, Linux and Mac OS X. It ships with user interfaces for Qt/KDE, Gtk/GNOME, Tk and a command line. There will hopefully be native user interfaces for Windows and the Mac soon, until then, the Tk interface works on those platforms.