Well, it depends a lot on your individual circumstances as a organisation but the Swedish Medical Center in Seattle have managed to do save $1,000,000. Their IT is quite big with 500 applications across 4,500 desktops and 150 thin desktops and they have just over 7200 employees.
They made their savings by being smart about the management of their IT Infrastructure and also utilising some of the latest technology out there including SoftGrid which allows you to deploy almost any application to any desktop. They've got a case study on Microsoft.com which is worth exploring for more information.
What is SoftGrid and how does it work? It's probably best explained by watching the guided tour. When I saw this technology I have to say that I was impressed. It's very interesting how this is going to slot in with the whole Software + Services model and desktop vs webtop debate. If you can take your applications wherever you are, whatever machine you're on, then where do web apps fit in?