Instagram, now owned by Facebook, is a massively popular social photo sharing network that's more recently expanded into video and messaging as well. With Instagram you can take photos, scale and crop them down to a square aspect ratio, rotate, add blur, filters, and framing, and post them to your timeline or send them directly to friends. You can also record crop, filter, and post video.
Currently Instagram supports direct posting to both Twitter and Facebook. You can also use the Photo Map feature in Instagram in order to view all of your photos in a map view. Over time Instagram has added more filters and more editing tools for users to take advantage of. In order to compete with other photo sharing services and replacement Camera apps, Instagram has added more and more powerful editing tools to ensure it's your one stop shop for taking, editing, and sharing your images. Recent updates to the Instagram app itself have included advanced editing options such as exposure, sharpening, warmth, saturation, and more.
Instagram videos can be anywhere from 3 to 15 seconds in length. You can either take a new video or import existing video and select the portions you'd like Instagram to use. You can then add filters just as you would to a still photo. Most recently, the direct messaging feature of Instagram lets you send private photos and videos to your friends without having to post them to your Instagram timeline.
Instagram has yet to ship an iPad-optimized version, though the iPhone version can be run on the iPad.