Called "A collaborative rubric toolkit," the search engine will help you find a pre-created rubric, and has K-6 rubric sam[les for assessing student writing as well.
"4Teachers.org works to help you integrate technology into your classroom by offering online tools and resources. This site helps teachers locate and create ready-to-use Web lessons, quizzes, rubrics and classroom calendars. There are also tools for student use." Loads of tools.