Apple users, you might want to check your Software Update. There's a 143.59 MB operating system update waiting for you. We don't usually report about these incremental updates, but this one is attached to a notable new feature which arrives with the your operating system package: the Mac App Store.
Think of the Mac App Store as the same thing as your iTunes/iOS app store, except this one is designed for your computer (and thus lauches as an actual application and not in iTunes). There's about 1,000 apps (mix of free and paid applications) available at launch, with the Mac App Store requiring you update to Mac OS X 10.6.6, available for download via Software Update or via this link.
After installing the update, look in your dock or in your Applications folder and you'll find a circular blue "A" icon. You'll log-in with your Apple ID info and then away you go; browsing is very similar to the iTunes store experience, and there is the option so search by categories, free/paid, What's Hot, Staff Favorites. We downloaded the new Twitter app (free) and it was an extremely simple experience, though we were underwhelmed by the actual app itself. We expect Apple will be tweaking/modifying this Mac App Store in the same way the iOS app experience has evolved.