Choose an avatar and type (text-to-speech) or record your voice. The app creates an animation. You can also customize the background with photos or drawing. You can share the animations using Facebook, Twitter, email, text message, or URL.
Limitations: Free as of 3/5/2014, but may become a paid app.
Create a short video by taking a photo and recording your voice. You indicate where the mouth should go, and the mouth is animated for you. You can also add stickers, frames, text and photo effects.
ChatterPix (https://itunes.apple.com/us/app/chatterpix-by-duck-duck-moose/id734038526?mt=8) is the same app, but aimed at adults instead of kids.
Limitations: Non-Roman characters not accepted in the text input.