Last week, Apple released OS X version 10.6.6, of which the main feature is the Mac App Store.
The about Mac OS X v10.6.6. Update document describes how to update.
In addition to the Mac App Store, this update also contains an Apple security updates: a fix for a PackageKit man-in-the-middle vulnerability.
Download: Mac OS X v10.6.6 Update (or perform an automatic download)
–jeroen
