Windows Live ID is the authentication tool that is part of the Windows Live Service. With it you get free email, blog page, photo galleries, document storage, and more. Social networking tools such as Groups are also available. Groups allow you to invite people to participate in discussions, document sharing, events and calendars, and more.
Microsoft Dynamics CRM Online uses the Windows Live ID ( WLID ) to authentication who the user is. You can also integrate the Windows Services with your Microsoft Dynamics CRM application.
Integration with the Windows Live Service can enhance your CRM experience. Using the document storage service, Sky Drive, can allow you to share documents with other users and people not in your CRM system such as customers, business partners, and colleagues.
I’ve created a video that will introduce you to Windows Live ID and it’s services. The video also shows how you can use Windows Live Groups and Document Storage with Microsoft Dynamics CRM.
Windows Live ID Overview
How to integrate your Windows Service Storage - SkyDrive with CRM Online
Also, you'll want to watch the video by fellow technology specialist Kevin Williamson on how to add users to Microsoft Dynamics CRM Online.