http://www.baker-evans.com/community/course/view.php?id=20 (opens in a new window)
It uses the existing "show only topic ?" blue boxes (which new users get confused with) and thus remembers the state you left it in. It ain't a perfect solution but it is a workable one and does not require you to to have admin access or install any new themes or blocks.
Any feedback gratefully received.