Skype allows users to communicate with peers by voice, video, and instant messaging over the Internet
Features and improvements of Skype 5.8 for Windows are:

Full HD video-calling
Support for Facebook audio and video-calling (beta)
Group screen sharing
Hide offline Facebook contacts
Push to Talk
Skype updater service
Bing Toolbar integration
Full HD video-calling

Now you can make crystal clear video-calls with your loved ones or business contacts by utilizing the latest technology for Skype and Logitech, which is incorporated into the latest update to Skype for Windows and the Logitech C920 webcam.

With Logitech c920 the video encoding is done inside the camera which enables full HD or HD video quality with older computers. To enjoy full HD quality at its best, you will need at least a 2 Mbps upload/download speed.

Group screen share

Group screen sharing allows users to share their entire screen or a single application window with other participants on a conference call while continuing to stream video. To start a group screen share, choose the + menu during a call and select "share my screen." Group screen sharing is available with Skype Premium, which also includes Group video calling and live chat customer support.

Video calling to Facebook users

Now you can make video calls with all of your friends on Facebook, even if they aren't Skype users. To start a video call with a Facebook friend, select the person in your list and click "video call."

Push to Talk

We have introduced a "Push to Talk" feature in Skype. Many people who are playing multiplayer games have requested this feature, which allows users to set a hotkey to toggle microphone muting on a Skype call. You can set the "Push to Talk" up on the hotkey's selection under tools > options > advanced > hotkeys.

Full release notes for the Skype 5.8.0.154 for Windows are:

New features and improvements:

Full HD video-calling
Support for Facebook audio and video-calling (beta)
Group screen sharing
Hide offline Facebook contacts
Push to Talk
Skype updater service
Bing Toolbar integration

Fixed issues:

Accessibility Active call plus menu focusing was not correct
Calling Seldomly in compact mode call duration was not displayed
Group conversations It was not possible to add a phone number to a group which belonged to a Facebook contact
Options Proxy settings in client were not disabled when proxy was set using registry keys

http://www.skype.com/intl/en/get-skype/on-your-computer/windows/

A Guy