How can I share my desktop using Skype?

When you are in a video call, you can share your desktop by click on the video button (as in the picture) then click share your screen>choose what to share.

With the latest version of Skype for Ubuntu, sharing your screen is activated differently.

You can either:

In a call: hit the + button in the call window > Share screens

Or...

Right click on a contact name > Share your screen... > Share full screen or Share selection