I controlled the most visited site of all 11 sites, including all the back-end code, but after a couple of planning meetings, it was pretty clear what needed to be done, and my own transition was pretty flawless. Organization-wide, we went from FTP servers, different CMS products (including a few home-grown ones), and people hand-coding everything to a single site and single CMS in a very short time. It's got fully functional blogs, status updates, and live feeds, plus every person who needs to can have access to their own small part of the site. It met *every* need we had, for a very broadly technology group.
The whole thing was a 6 month project. We didn't hire any outside contractors, and people (a tiny handful, really) just did the work as part of their jobs. The key was having someone competent orchestrate the entire thing: someone who understood the project management aspects and knew how to use her resources. I felt a bit bad for her: she didn't have a team to work with her, but she certainly pulled it off. Compared to other web-dev projects I've seen, even ones with teams in the dozens and with outside contractors, this was pretty spectacular.
I don't often post about the stuff I do at work: most people don't care. But I was in there today, editing away in our new CMS (SilverStripe, for those curious), marveling at how well the whole thing works, and how clean it is. I learned a whole lot from the process: skills that serve me quite well on the current web projects I host. I was just amazed at how well it went, this project that ended last year, and wanted to post, because really, learned so much about quality web development from it.
The website, for those interested, is http://ocio.osu.edu/, and the "software" pages are mine.