First you will need to make sure you have libv4l-0 installed.
If you have installed Ubuntu restricted extras then you should already have it if not open Software Centre and install Ubuntu restricted extras from there.
Once this is done open a Terminal and copy and paste the following command
sudo gedit /usr/share/applications/skype.desktop
After you have provided your password a text editor will open.
Line 4 should look like this
Replace with this text
Exec=bash -c 'LD_PRELOAD=/usr/lib/i386-linux-gnu/libv4l/v4l1compat.so skype'
Save and exit the text editor and close the terminal. Now you can open Skype and test your webcam via 'options' then 'video devices'