At WWDC Keynote on June 6, Apple officially unveiled Mac OS X Lion, the eighth major release of Mac OS X.

It was announced that Max OSX Lion will be available at $29.99 as a 4GB download exclusively in the Mac App Store. The price is $100 less than typical upgrades making it the easiest upgrade ever.

Lion will be available today for developers in preview, and out for consumers in July.

With more than 250 new features, here are the top 10 that were outlined during the keynote:

The Mac App Store - The Mac App Store is currently the No.1 channel for Mac software, offering apps for browsing and purchasing. Newly purchased apps install in one step and appear right in the new Launchpad. In Lion, a new feature will be coming to the App Store, allowing in-app purchase. Using your iTunes account, you can purchase upgrades or add-ons from within the app itself.

Full-screen apps - Like on iPad, every app will be displayed full screen. You can make a window in an app full screen with a single click, switch to another app's full-screen window by swiping the trackpad, and get back to the desktop with another swipe. Developers can take advantage of full-screen technology in making their apps.

Auto Save - Lion will automatically save documents while you work, and starts where you left off the next time you open the document. You can choose to revert to the last opened version, or lock your work to prevent it from being written over.

Versions - Versions record the progress of a document, and allows you to see older versions of your work. If you need to revert to an older version or retrieve part of a document, a cascade of previous versions will give you access to the past versions, in a Time Machine-like interface. You can copy and paste work from a previous version into the updated version.

Multi-touch gestures - A richer multi-touch experience allows you to enjoy more fluid and realistic gesture responses, including rubber-band scrolling, page and image zoom, and full-screen swiping.

Resume - With Resume, you can restart your Mac and return to what you were doing before, with all your apps back in the exact places you left them.

Mac Mail Version 5 - Mail 5 features a new layout. You see the messages in your inbox as well as a full-height preview of the selected message. The new version also includes a new way of the search new Maibox bar, and Conversations, which automatically group messages from the same conversation.

AirDrop - This Drop-box type feature allows you to send documents to any computer around you, wirelessly, by clicking the AirDrop icon in the Finder sidebar and dragging the file to the recipient's name.

Launchpad- Like the iPad, you will get instant access to your apps. With a pinch gesture on the trackpad, all the applications will fly on your screen, making it a lot simpler to find applications. You can easily move apps around in the Dashboard.

Mission Control - Mission Control provides you with a bird's eye view of what's going on in your Mac. With a simple swipe, your desktop will zoom out to Mission Control, and you can see your open windows grouped by app, thumnails of your full-screen apps, and Dashboard.