To install Skype on an AMD-64 system, you'll need the 32-bit libraries (if you're distro is 32-bit, skip this bit),

sudo apt-get install ia32-libs

Now grab the qt4 libraries,

sudo apt-get install libqt4-gui libqt4-core

Download the appropriate Skype package from...

• Skype Linux

Firefox should download it to your desktop so...

cd Desktop
sudo dpkg --install --force-architecture --force-depends skype-debian_2.0.0.72-1_i386.deb

And you're done, with the Webcam driver installed and enabled you should now be able to make video calls too.

• Ubuntu Webcam Install