The new Mac App Store is online
It’s simple way to find, install, and manage your favorite software. To see the Mac App Store at all, you’ll need to run your Software Updates (under the Apple menu) and get Mac OS X 10.6.6 System Update, or run the combo update you can download here.
After you reboot, you’ll see a new icon in your dock, right after the Finder icon. Click that to launch the app store. Most apps cost less than you may have seen them at retail, but some, like Things, are priced higher than we’ve seen them in bundles.