Heidi Goodrich, a rubrics expert, defines a rubric as "a scoring tool that lists the criteria for a piece of work or 'what counts'

Rubistar - Create and modify rubrics, site includes tutorial and rubric templates.

Kathy Schrock's Guide for Educators - A variety of rubric and assessment information.

Teach-nology - Rubric generators for math, listening, writing and many other subject areas.

Education World - Rubric article titled, "Creating Rubrics: Tools You Can Use, includes links to additional rubric sites.
Rubrics - Examples of rubrics, graphic organizer templates and many other teacher resources.