Microsoft SharePoint (Document Management)
"Microsoft SharePoint 2010 and Microsoft Dynamics CRM 2011 is a match made in document management heaven. With SharePoint 2010 installed along with a special SharePoint list part and a few configuration items set in CRM 2011 you can have document folders set up automatically in SharePoint when you create entities in CRM. And documents created, updated, and saved in those SharePoint folders will be available in CRM. Plus you can do this integration with a combination of on premise and online solutions between the two products." - Source: CRM Software Blog
SharePoint and xRM
