Apple has announced iTunes in the Cloud is now available. This feature allows you to download music to one device and have the music automatically appear on all of your devices. If you buy a song on your Mac, it will be on your iPad or iPhone. This feature will work over Wi-Fi of 3G. You will need to install the latest version of iTunes and iOS5 on your devices.
You can also download past purchases made from iTunes. iCloud stores your purchase history so you can download what you want from any of your devices or choose not to download certain items.
iTunes match is still “coming soon.” This feature, for a fee, will allow you to replace music you have imported into iTunes with items available in the iTunes store (if the items is there.)
Right now, Apple iTunes will allow you to stream, for free, on your computer, one new song every day until Coldplay’s newest album is released October 24.
If you have a large iTunes library on your Mac and don’t want to load your iPad (or iPhone, iPad2) up with all the music, you can use Apple’s Home Sharing to stream the files from your Mac to your iOS device. (You need to be on the same Wi-Fi network.) Here’s how…
First, you need to turn “Home Sharing” on your Mac in iTunes. Open iTunes and under the file menu Advanced > Turn on Home Sharing. Enter your information (iTunes Account name (Apple ID) and password).
After you enter the information correctly in iTunes, you will receive a message that Home Sharing is now on. You will need to use the same Apple ID or account when turning on Home Sharing on the other devices.
Next, you will need to turn on the sharing feature on your iOS device. The place to do that is on your iOS device. Choose Settings > iPod. You will need to enter the Apple ID and Password.
[ NOTE: iOS5 has modified the settings. You now need to select Music instead of iPod. ]
Last, you need to open the iPod App on your iOS device with iTunes open on your Mac.
When you do this, you should see “Library” on the top left. Tap once to pull up the “Home Sharing” libraries available.
Tap the library you want to stream to your iOS device. Then select and play the music. It will play on your iOS device as if you were in front of your Mac.
If you need to review the Apple Knowledge Base Article on this, you can do so here.
Right now, it does not appear that you can stream videos from your Mac to your iOS device.