Emily, you can't read during the Shred or Biggest Loser DVDs, but I have to admit: I've occasionally turned the sound down and listened to a podcast. It wouldn't work with a new DVD, but if you're doing one you're familiar with, it's not that hard.
I don't do it that often, because I don't really like the breaks in my concentration it seems to engender. But every once in awhile, when fear of boredom is what's really keeping me from doing the workout, it's worth it.
I imagine you could do the same thing with a book on CD.
Or music you like. But I haven't tried that yet. I should though. Most workout DVD music leaves a lot to be desired. I want to work out to Shakira! :D
btw, anyone else watching the World Cup? Now that's fitness!