After some recent software updates, my SuperDrive simply stopped mounting DVDs. A Google search pointed (at last) to the solution: PatchBurn, "...a program that generates and installs so called device profiles for CD/DVD-burners". I downloaded that program, ran it, and rebooted. After that, my SuperDrive worked correctly.
[robg adds: PatchBurn is typically used to add support for third-party burners to OS X -- it's use in that context was covered in this hint. It's also been mentioned in a number of comments over the years. This is the first I've heard of it being used to repair a stock SuperDrive, however.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20061103105911200