Windows Live Messenger 8.1.

Windows Live Messenger 8.1 includes support for the im Initiative! Every time you start a conversation using im, Microsoft shares a portion of the program's advertising revenue with some of the world's most effective organizations dedicated to social causes. So any time you have an im conversation using Windows Live Messenger 8.1, you help address the issues you feel most passionate about.
It's simple. All you have to do is join and start an instant messaging conversation. Join now at http://im.live.com.

Key Features:
Call your friends' PC (free), mobile or landline phones.
Calls require a microphone and speakers or a headset and broadband connection.
Make calls for less than $.02 a minute to most places around the world with Verizon Web Calling.
Start a video conversation within minutes with a webcam.
Drop in photos and other stuff for friends in a Sharing Folder, as many as your computer can handle.
With Windows Live Messenger you can now connect with your Yahoo! IM contacts. you can free download Windows Live Messenger 8.1 now.