Practically everyone here at Apartment Therapy is a rabid iOS Instagram user. In fact, I may be the late and lone Android edition Instagrammer at the moment (temporarily, as it's a loaner). But even after a week, I recognize why the app has long been a staple on "must download" lists amongst iOS users. And if you really love Instagram, you can now share the best of your best images as an iPhone case! Each Casetagram snap on, hard case is available in black, white, or transparent for $34.95, compatible with both the iPhone 4 and newer 4S model.
If you're not committed to ordering, you can at least play around with the demo, which pulls images from your Instagram feed and allows you to layout a sample design via web UI so you know what you'll be getting (just watch out, the process of composing your case can eat away the minutes faster than you expect, such is the addictive nature of trying out every design/photo combination).