Recently, I discussed web applications as one way to simplify an environment in preparation for moving an organization to Linux. People sometimes forget this option. Do you have applications that can run via the web? Maybe you have a group calendar system that also has a "web client". This can be an easy way to remove an obstacle to your Linux migration. If you have any applications that are "Windows only", check if there is a web option available to you.
This raises an issue that Microsoft feared back in the late 1990's. It's why Microsoft fought so aggressively to get into the web browser market after first ignoring it. The operating system platform matters a lot less if people consume applications via the web rather than through the desktop. It's awfully hard to lock users to Windows when they don't run any Windows apps per se.
In one example, when I first ran Linux at work in my current organization, our groupware application was advertised as "Windows-only". But I found the web version worked perfectly on Linux using Firefox, so I got along fine and had no problems interacting with my co-workers via the groupware.
A glaring example today is Google Docs. Available via the web to any capable browser (including some mobile platforms), you can edit documents, work on spreadsheets, and create presentations. It has the look and feel of previous versions of Office, without that Ribbon interface.
Sure, your very advanced users will find certain "power features" missing from Google Docs. But it does the job well enough for today's office environments. My work adopted Google early this year. After experimenting these last few months, I found myself gravitating to Google Docs for all my work. I'm a manager, so most of my office work is writing strategy documents or managing budget spreadsheets, with an occasional presentation. Surprise! I can do all that from within Google Docs. And it doesn't matter if I'm running Windows or Linux.
As an added bonus, many of us at work now collaborate remotely when working on documents and spreadsheets. The other person might be in another building or another state, but we can still have the same document open to add our changes, and use a text chat system to ask questions. It was a little odd when I first did this, but now it's become the new norm.
This scares Microsoft to death. I'm sure there are lots of meetings in Redmond that ask the question, "If people can use all these apps from a web browser, why do they need Windows?"