If you have not seen the 100 Word Challenge website I suggest you check it out. This is run by the amazing Julia Skinner (@TheHeadOffice) and is a weekly writing challenge for students.
Students are given a motivation - this could be a picture, part of a sentence, or a few words - at the start of the week to help them write a 100 word piece of writing. That is it - 100 words! It is great to get my boys writing as you can do so much teaching with 100 words and it doesn't take them long. Students then upload the piece of writing to their blog - or class blog (this will be my next blog post) and then add the link to the 100WC website.
From this link other teachers and students can see it and your students will get feedback from people around the world. Each week their is a SHOWCASE and this highlights the best pieces of writing. Here is a piece of writing from a girl in my class that was 'showcased' and from that I got many tweets from educators around the world praising the student. I shared these with the student and it made her term!
There is also a twitter chat each week and you are now able to join 'Hubs', although I have not done this yet. Joining a hub puts you in contact with several other classes around the world and then you can comment on each other's writing.