Scenes from Apple's WWDC keynote address (photos)

Apple CEO Steve Jobs took the stage this morning to kick off the company's Worldwide Developers Conference in San Francisco. He quickly handed things over to Phil Schiller, Apple's senior vice president of worldwide product marketing, to talk about the new version of Mac OS, dubbed Lion. He then introduced Scott Forstall to talk about iOS 5.

Almost 90 minutes later, Jobs returned to the stage (shown here) to discuss Apple's new iCloud services.

Click on for more slides from the presentation, or for more details, see our live blog and a list related stories.

Schiller goes over 10 features in Mac OS X Lion, including full-screen applications.

Lion also comes with support for multitouch gestures, including tap-to-zoom, two-finger swiping, and more. That functionality has helped Apple nix scroll bars, which will show up only when users scroll using the new gestures.

New features are also added to redesigned Mail, including a two- and three-column view and a "conversation view," which groups together similar messages so you can see how it flows.

Other new features in Lion include a new migration tool for Windows users, a Safari reading list, and push notifications, Schiller says.

Lion will be available to customers in July as a Mac App Store download, Schiller says.

Most major releases have cost $129. But Lion will be just $29.99, because "we love it so much," he said.

Forstall hits on 10 new features in iOS 5, one of which, Newstand, is aimed at helping users manage purchased digital magazines and newspapers from their iOS-based device.

Another iOS feature is the integration of Twitter into Camera, Photos, and other apps, allowing users to quickly tweet from the native programs.

The Reminders app brings the capability to store multiple lists with dates for each event and categorize reminders by location. So for example, if you have a reminder of "Call home when I leave work," the app notes that you're on the move.

Forstall talks up how popular the iPhone 4 has become on Flickr.

Forstall says a lot of people who are buying these devices don't have computers. So iOS 5 delivers over-the-air software updates. In addition, iPhone buyers will no longer need to tether their smartphone to their computer to activate it; all that will be done on the device.

The company's new iCloud service will be supported by new versions of applications including Calendar, Mail, and Contacts, so if information is changed for one contact, it goes to Apple's servers and and then is pushed to the other devices. Cloud backup is another part of the service, including daily wireless backup of an iOS device. Third-party apps can also store documents in the cloud through new interfaces that will be made available to developers. Everyone gets 5GB of free storage on Apple's servers for mail, documents, and backup purposes, but purchased music or books don't count toward that limit.

One of the three most amazing and inventive parts of iCloud, Jobs says, is the Documents app, which keeps files in sync across multiple devices by pushing the updates. (The versions that went out last week secretly had this feature included, he says.)

Jobs says the second most inventive iCloud app (and "maybe" Jobs' favorite), is Photo Stream, which brings your entire camera roll to the cloud, then syncs it with other devices.

It includes photos you've taken, as well as photos that have been imported to the camera roll through something like Apple's camera accessory. It will use iPhoto on the Mac, the Pictures directory under Windows, and be integrated into Apple TV. (On iOS, the last 1,000 photos are stored.)

The third iCloud app Jobs touts is iTunes in the Cloud, which among other things, lets you see a history of songs you've bought, even if they were purchased on another device.

You can re-download any of the albums or songs you've bought, Jobs says.

Job's customary "one more thing" item is a service called iTunes Match, "iTunes Match," which allows users to store their "entire collection," including music ripped from CDs, on iCloud servers for $24.99 a year. It works by analyzing songs in your collection, comparing them against the 18 million songs in the iTunes Store, and then making those available immediately at 256 Kbps, even if the originals were lower quality.

"If you don' think we're serious about this, you're wrong," Jobs says, concluding the event. Then he shows photos of the newly constructed data center in Maiden, N.C.

Jobs gets huge applause when he takes the stage at the start of the keynote address. Here, he interacts with someone in the crowd.

The line of people waiting to get into the keynote address at Moscone Center.