Rubrics
Very simply put, a rubric is a scoring guide or a grading criteria. It is “a scoring tool that lays out the specific expectations for an assignment” (Stevens and Levi, 2005). Rubrics list the criteria that you are looking for and the levels of achievement (or scale or gradations of quality) along those criteria. Rubrics not only help students understand your expectations, but can make grading faster, easier, more accurate and consistent. In cases where there are multiple graders (like TA's) this consitency is especially important.
Useful Resources
Rubrics: Jon Mueller
Introduction to Rubrics:Carrie Zelna and Ted Elling
Software for Rubric Creation
Teachnology: Has several Rubric Makers and examples of Rubrics (K-12 related)
Further Reading:
Stevens, D.D. and Levi, A.J. (2005). Introduction to Rubrics. Stylus Publishing, LLC Sterling, VA