I know that people still look at you askance when you use the words "Microsoft" and "open source" in the same sentence, unless, of course, you are discussing litigation. But while Microsoft actually has a long history of both participating and litigating the open source community, they do actually have a few very active projects, primarily focused around issues with Hyper-V and virtualization, where they make a significant effort to get community involvement.
One of these significant efforts is the cloud management tool that was formerly a product known as the DotNetPanel, which was acquired by Microsoft and released into the open source community as the WebSitePanel project, a management component that integrates with the Dynamic Datacenter Toolkit, which itself is a key component of the Hyper-V based cloud model.
One of the Microsoft Gold Partners that worked on the Dynamic Datacenter Toolkit development with Microsoft announced this weekend that they had integrated the WebsitePanel open source into their own Hyper-V hosted cloud. Managing and provisioning VMs is a task that is most often undertaken using dedicated, expensive proprietary software solutions, but virtualized hosting provider Applied Innovations has integrated WebsitePanel into their Virtualization environment. This allows their Hyper-V hosted clients to create and manage new VMs from directly within their management interface.
AI went with the open source WebsitePanel because they believed that they would get a heads-up on their competition by enabling this management capability for their Microsoft cloud by not waiting for third-party applications. They decided to integrate the open source project along with the work they were already doing to enable their cloud customers to create and manage new VMs. They were looking to deliver a unique and useful solution that provided a good value-add for their hosting services and well-served their customer needs.