I recently got an iPhone and have been trying out lots of photography apps. A new favorite is ToonCamera. You can shoot movies or take photos in a few cartoon and sketch styles. There are also basic adjustments you can make to the styles. The view finder shows the cartoon style, so you can see what the finished image will look like as you shoot. A very fun, easy-to-use app reasonably priced.
Here is a short video I shot of our dog Chloe.