Here’s a video Marty Soupcoff (Instructional Technologist at California State University, Northridge) made as a response to a posting at Moodle.org (http://moodle.org/mod/forum/discuss.php?d=201561) which was asking for how to create a gradebook calculation and weighting of grades. Pretty informative. Follow the Moodle.org link to read up on the scenario.
Just another great example of the Moodle community.
Direct video link: http://www.youtube.com/watch?v=r3dT_DqUjBs