Looking for some sysadmins in large multi-national orgs.

I work for a large multinational education corporation. We have offices and schools all over the world. Many back offices that support different schools in different countries. Some schools are partners some are owned by us. We are re-evaluating several aspects of our infrastructure such as separating our active directory and how we deliver applications. So how do you do it? What does your AD structure look like? How do you manage hundreds of applications? How do you handle authentication for the apps? Have you gotten sucked into the "cloud" yet?