When faced with the expectation that I attend non-productive meetings, I go, but spend most of that time working on strategies for making it through the next several hours. Feel free to use or adapt any of my coping mechanisms.
Tried and true:
Count the number of people apart from you also not paying attention. Generally, this will be everyone but the person talking.
Imagine everyone in their underwear. If two or more look appealing, arrange an after work get together.
Work out the choreography in your head for a movie scene where you all break out in song, preferably to something funky like Car Wash by Rose Royce (mp3).
Keep a count of all word bastardizations (1. laxadaisacal 2. asterik 3. I think there was another but I stopped listening)
Try and figure out where you could have possibly heard the word ridonkulous.
Saving for a special occasion:
Leave the room and go get a haircut or change clothes and see if anyone notices on your return.