I'm pleased to announce that Moodle 2.2, due for release on 1st December 2011, will include the new feature rubrics for grading assignments.
A rubric consists of a set of criteria, each with several levels. A grade is calculated based on the levels selected.
Rubrics is part of the advanced grading methods feature developed by David Mudrak and Marina Glancy from Moodle HQ. Thanks to everyone who joined the discussion Request for comments: Advanced grading methods (like Rubrics) in Moodle 2.2.
It is hoped that in future versions of Moodle, rubrics will be available for grading other activities, such as glossaries and databases.
For further details of rubrics, see the documentation Advanced grading methods and Rubrics and also the screencast by Mary Cooch.