Maplin sells this USB VoIP phone for only £6.98 at Maplin.
It supports the popular Skype VoIP software as well as others.
It is fully compliant with USB2.0, comes with 10 customised ring tones and has a Magnetic hook for convenient storage.
You can plug it into your USB port and make free* internet calls using a compatible VoIP service provider. The only issue you might have is with its colour - Lime Green; no other colours available.