I have had the same question and hope to get some discussion going on options (or potential upgrades). Drew's solution works if you (a) don't teach that many courses or (b) "retire" courses after running them. Otherwise, you will end up with dozens of the same course listed over and over again. We don't yet teach that many courses, but we intend to, and we want to save our old courses.
I have been using "Groups" so that different course instances do not appear as new courses. For example, for our Course "Basic Lawyering Skills" we have for Groups "Basic Lawyering Skills 2005," "Basic Lawyering Skills 2006a," etc.
However, this is less than ideal because each time we run the courses, we need to update all the dates, etc. associated with each course. That then screws up the course dates for previous participants, which is OK so long as we are not running two overlapping but not coterminous courses.
Does anyone else use Moodle in the way we describe and have a better solution?