Writing Sites for creating books and comic strips:

Create a Silly Story

Kerpoof

Read Write Think - Nice drawing style in this one.

Toondoo - Flash based and if you sign up you can embed the strips into your blog. (This one is for older students - make sure you read the 'terms of service' and check with your parents before signing up).

Make Belief Comics - This is my favourite.

ComicStripcreator - lots of options on this one, not able to save without an account.

Comic Strip Generator - Very interesting style used in this one and able to print

Captain Underpants - Just press the start button for a little toilet humour :) Not sure if this interest students or is good for the education environment!

My Story Maker walks the students through creating a book