Get your head in the iCloud today
Apple didn't waste any time pushing some of the new iCloud features to iOS devices. Just a few hours after the end of the keynote presentation at the Worldwide Developers Conference yesterday, users began seeing some iCloud features in the App Store. If you are running iOS 4.3 or above, open the App Store and select "Updates." A new "Purchased" button is at the top of the screen and when you select it you'll see the screen below. From there you can view all the apps downloaded with your account. The ones marked with a cloud are stored in your iCloud account and can be downloaded again, on up to ten devices, without additional charges. You also can view all the downloaded apps that are not installed on the device you're using and use the search function to find purchased apps by name. These features didn't show up for me until I updated my iPhone to iOS 4.3.3, so if you don't see them you might try updating.
You also can try the new iTunes in the Cloud feature by downloading iTunes 10.3 which is available for pubic beta testing. As it is with all beta software, however, use caution and backup up important files in your iTunes library (personal recordings, for instance) before installing the update.