Tony Ruscoe likes to snoop around Google just as much as myself, and just today he stumbled across some interesting login screens that nobody has seen before. Right now, these services are still just acronyms that could stand for anything -- and there is no guarantee they aren't remnants of services that have already been launched.
Users in the blogoscoped forums have been talking about these findings, and they have been speculating what these services might actually be.
The best guess so far, that seems to be aligned with Google's goals, is Simple Storefront Distribution. This guess stems from a Google Group that seems to describe Simple Storefront Distribution and has a link to www.simplestorefront.org.
Well, we already know what MDC means -- Mobile Download Console. This is known because when you go to the login screen, the definition is seen directly above where you type. When Tony tried logging into this service, he found a screen remarkably similar to a Google Base error message. It's unclear how MDC and Google Base are related.