This is a great website that I heard about when I was at my "Critical Thinking and Technology" workshop at the board. Storybird is a flash-based web page that has fantastic art from artists around the world. You are invited to choose the artwork of an artist that interests you, and then you use it to author a story. A teacher can set up a class account and add their students to their account (somewhat similar to Bitstrips). There is a decent variety of art to choose from, and it is free. There is an option to purchase a hard copy of the book you create.
Here is the cover of the first Storybird Book I created:
Here is the link to go to if you would like to read the book:
Here is another story:
Here is the website: