Currently, I'm going through a 30-day trial with ComicLife2 (no affiliate link).
I find this app useful for creating images with captions that can be shared on facebook and Pinterest. But you can also create comic strips or even comic books.
You can use your photos or graphics. The interface is very intuitive.
If you like it, you can register and pay $29.95.
The download for the trial period is free and instant, and you don't have to fill out any (credit card) info.
I just got it yesterday. This is my first strip, using my own Doodlebug graphic.
You think this is funny?
(Click to enlarge)