When it comes to embracing social technologies for business - Dell is an organization that is always a case study for the various communities it has created. Starting with almost a negative brand - Dell has leveraged conversations, community and collective intelligence using its properties like Idea Storm (a platform where anyone can submit ideas - and they are voted on by the community - and then chosen ideas are implemented)
Dell also has a vibrant support community - where users solve other users queries about Dell products. Then there's a vertical community for Small and Medium Business Owners, where SMB owners get advice from other entrepreneurs on running their business.
Then of course, there are the "social outposts" on Twitter like the DellOutlet which has helped Dell USA earn millions of dollars in revenue, and the SMB page on Facebook.
Check out Dell's slideshows that explain how Dell engages with the tools and listens and reaches out social media, blogging and responding.
Disclaimer: I am a Dell Alumni - having worked there as a HR generalist in 2005. In addition, my current employer 2020 Social works with Dell on their social media initiatives, like Dell Go Green - although I am not part of the team working with Dell.