Quill.org—Interactive Writing and Grammar
Quill.org is a non-profit website offering over 140 grammar and writing activities. These activities are entirely free and cover 42 Common Core Standards for grades 1-8.
Currently, Quill has two activity types. In the first, Passage Proofreading, students are tasked with finding and correcting grammatical errors in a passage. Then they receive a personalized lesson based off of the concepts that they missed. In the second type, Sentence Writing, students rewrite grammatically incorrect sentences properly.
You can try a sample activity right on the Quill.org homepage without logging in or registering.
Quill also features a lightweight learning management system. Teachers can use this to assign lessons, monitor student progress, and manage their classrooms.
A collaborative vocabulary and writing application is also in development. If you would like to test it, please send an email to email@example.com.