Ever take a really awesome photo on your iPhone only to find out it doesn't translate well to Instagram as a square photo? Yeah, we've all been there. While you could always settle for a cropped version, you don't have to. With the help of another App Store app you can post your photos to Instagram in their original aspect ratio.
There are lots of App Store apps that allow you to add borders and upload non-square photos to Instagram photos. My favorite is InstaSize because it's easy to use. Also: it's free. There are ads but if you like it enough, you can remove them forever for a nominal IAP via the Settings section.