You will need to install MorphVOX Jr'. The software which intended to change voice... which is funny things too, but we need it's ability to pass sound unchanged. After installation it will add a virtual sound source into your Windows -- 'Screaming Bee Audio Driver'.
After initial calibration configure MorphVOX Jr this way:
Make sure you have no Push-to-Talk enabled:
And you have Morph and Listen switched OFF:
In Windows Sound Mixer set the following in Recording options:
And finally in Skype set Screaming Bee Audio Driver as source:
One side note: Please be aware that until you close MorphVOX Settings dialog it will not pass audio to the Skype (actually to it's driver).
Obviously, you have to have MorphVOX running in background to make SkypeCast working.