We will start to write story about our characters, and there is some suggestions about collaborative tools. Unfortunately, titanpad is about to close in May so we cannot use it but there is many different tools, which we can consider:

  - complex and visual web tool (you can try here, write on the left side and you have to choose Rich Text)

  - google.docs, not so visual but simple

 - it is simple, one of us starts and invite others, but it is too much academic

An interesting tool to use in collaborative way is Idroo a collaborative witheboard to use also with Skype

https://idroo.com/

P.S. While I am searching I found interesting tool http://www.carnegielibrary.org/storymaker/ worth to try with students ;)