If you're bored with the default filter options Instagram gives you, Landcam for iPhone can add a little variety to your photos. You can also natively edit things like exposure and brightness before exporting your photo straight to Instagram.
Landcam supports sharing photos to social services such as Instagram, Facebook, Twitter, email, and more. You can choose to take your photos within Landcam or you can import existing photos from your camera roll.
There are certain filters within Landcam that you'll have to unlock in order to use but you won't have to pay for them. Just like the Landcam page on Facebook and you'll have access to the premium filters. I've found a lot of the filters in Landcam to be less obvious and more subtle than Instagram and other apps. If you prefer filters that aren't as dramatic, it's a better photo editing option.
If you happen to give Landcam a try, let us know what you think.