Local author Kate Messner, who spoke at our September 15th Children's Room event, hosts a virtual community of teachers who practice writing - because they want to practice what they teach. Check them out at Teachers Write!
Jo Knowles, who joined Kate on the 15th, also has a blog where she posts writing exercises every Monday.
The New York Times' Learning Blog has just added a new feature on Common Core Practice. Also from the same blog, this article on Writing Well - which should be read for the opening graphics if nothing else.
The above links are targeted for a teacher audience, the Young Writers' Project provides a whole range of tools for inspiring young writers and is focused on being a space where those young writers can collaborate.
Also for young writers, Kate recommends the book Spilling Ink which offers advice from today's authors to today's aspiring writers.