CaptionCam provides you with the easiest way to add captions to your photos:
https://itunes.apple.com/us/app/captioncam/id562126583

Just Snap, Cap, and Share

SNAP: Take a new photo or use an existing photo from you album

CAP: Add a caption to your photo

SHARE: Share your photo on Facebook, Twitter, Instagram, Email and more!

After adding your caption, you can MOVE, ROTATE, and RESIZE your caption as well as add multiple captions.