The App Store itself is a standalone app that looks a lot like iTunes. Apps are automatically dropped into the dock after download. Expect it to hit OS X 10.6 Snow Leopard users "within 90 days" from today. And developers? Apple's accepting app submissions starting in November.
Update: Apple's main site and developer site have been updated with App Store information pages, although there isn't much new to see beyond what was announced at the event.
Update 2: From the looks of that image above, individual iLife and iWork apps will be unbundled in the future for separate purchase. We're also wondering if this is the end of Apple Family Packs -- volume licensing that lets you install one copy of Apple software on up to five Apple-labeled computers -- after hearing Steve say that Mac App Store apps are "licensed for use on all your personal Macs?"
Check out our liveblog of Apple's Back to the Mac event right here.