Here's how you can download the Instagram app free for your iPad, iPhone, iPad mini or iPod Touch.
Download the Instagram App Free From iTunes
1. Go to the Instagram app preview page in iTunes.
2. Click the View in iTunes button.
3. Click the Free button to download the app.
4. Sync your iPad, iPhone, iPod Touch or iPad mini with iTunes to install the Instagram app.
Download the Instagram App Free From the iOS App Store
1. Open the App Store on your iPad, iPhone, iPod Touch or iPad mini.
2. Search for "Instagram" (without the quotes).
3. Tap the Free button to download the app and install it on your iOS device.
Here's a description and screenshot of Instagram for iOS devices:
"Pick from one of several gorgeous filtered effects or tilt-shift blur to breathe a new life into your mobile photos. Transform everyday moments into works of art you'll want to share with friends and family.
Share your photos in a simple photo stream with friends to see - and follow your friends' photos with the click of a single button. Every day you open up Instagram, you'll see new photos from your closest friends, and creative people from around the world.
100% free custom designed filters and borders such as XPro-II, Earlybird, Rise, Amaro, Hudson, Lo-fi, Sutro, Toaster, Brannan, Inkwell, Walden, Hefe, Nashville, 1977, and others.
Linear and Radial Tilt-Shift blur effects for extra depth of field.
Instant sharing to Facebook, Twitter, Flickr, Tumblr, Foursquare, and Posterous
Interact with friends through giving & receiving likes and comments
Full iPhone 4 front & back camera support
And much much more..."