One of key point Microsoft Pushed in WSS (Windows SharePoint Services) SPS (Office SharePoint Server 2007) is presence information, You can know the Messenger Status(Free, Busy,…) of the person who uploaded the information (Docs, Alerts, Announcements) in the WSS /SPS to collaborate.
Most of the time this presence information is marketed along with LCS. Instead of LCS this also works well with Live Messenger or windwos messenger (I have tested with yahoo but didn’t work well)
The simple thing which you can do to enable the same is provide the email id which you use in the Live / MSN Messenger in the email field of user properties of the Active Directory so that when the users are added to the WSS /SPS it will display the presence information of the user in the WSS / SPS Page.
Note: The presence information of federated (Yahoo 360) user is also displayed.