I've covered WriteReader in the past as an excellent learning tool to help students grades K-4 w/ their Reading and Writing. Recently, they have partnered w/ Sesame Street to allow students to create digital stories using their favorite characters (i.e. Big Bird, Grover, etc.). Once a student logs in they will see up to 20 characters to choose from to create their very own digital book.
I highly recommend checking out WriterReader by clicking here!!!