MobileMe as we know is going through some UI and feature overhauls, in selective beta, these past few weeks. The latest change in the web app is this beautiful in-your-face app switcher. Simply click the app icon in the top left, and this OS X-like HUD shows up on screen. Along with this change, the rest of the apps get the new deep blue toolbar treatment that first showed up in Mail.
Looks like the final version will be announced any time now.
UPDATE: My mistake. Apparently the new MobileMe is in full effect, out of beta.