I have mentioned already about my idea of creating a book. Yes, writing a book. But I know that it is hard, if there is no commitment and desire to create something like that.
Of course, that maybe, you must be thinking in a novel, but there is no need to do such a hard thing (no yet).
I will give you some ideas so your students can create a book.
1.- In groups, every student can create a couple of short poems. Let's see they create 6 or 7 short poems, they can have 24, 28 or even more poems per group. Then, if there are some students good at drawing, they can add some pictures and then they have their own booklet with poems.
2.- Every class, they can create paragraphs telling a story. With the time, they will have a long story to share with the rest of the class.
3.- They can create a blog, and adding posts as a journal or diary, so at the end of the month, they will get a collection of posts to create their own blog.
4.- There is an idea that I like so much. It is based on a teen series, where the student can create a manual to survive in the school, giving some tips and ideas to help students at school.
5.-Haikus are very short poems to be created not in Japanese, but in English.
6.-Twitter.... Yes twitter. OK maybe not all the students have twitter, but for instance, at a certain moment in the class, you can tell them to write a sentence about what they are doing, or thinking or watching. Then they will collect all these ideas as "thoughts in the class".
7.- They can create a book of "jokes". Students are good at telling goods, then tell them to write them all in English.
If you have more ideas, don't forget to share them.