The latest MacBook Pro and Air laptops are already for sale at the Apple store, but they won't ship with Mountain Lion (version 10.8). That update to Apple's operating system will be available next month for $20 for MacBook owners—and any system going back to Snow Leopard (10.6) will be upgradable.

Apple showed off a few of the new features of the operating system during today's keynote address at its Worldwide Developers Conference. Mountain Lion does a lot to integrate mobile-type features into the laptop environment. For example, you'll be able to respond to messages from your iPhone or iPad on your Mac. Reminders will be location-based. And of course, your mail, calendars, reminders, documents, and more are all synced in the cloud (online backup) across all your devices.

Other notable features of Mountain Lion include Power Nap, which updates and syncs compatible Apple laptops automatically when offline, using the least energy possible. Voice dictation will also be added with Mountain Lion. And AirPlay Mirroring eliminates the need for HDMI by pushing 1080p video wirelessly to TVs, and audio to AirPlay-compatible stereos.