Once your iPod or iPhone recognizes a track as an audiobook (see FAQ #1 for details), you have the ability to speed up or slow down the playback of the track. For people looking to power through a book (say, while driving to your book club), speeding up playback can be useful. For language learning, slowing down the playback can help to hear nuances of pronunciation and emphasis.
But the options provided by the iPod is not that great, just “Slower”, “Normal”, and “Faster”. Not a lot of control, and the speed change isn’t huge, in either direction. (And I find that it adds a nearly imperceptible but irritating clipping to speech). If you want to make an even bigger speed change, you need to turn to third-party tools that can process the tracks, and then sync the processed versions to your iPod or iPhone.
This is probably worth it only in extreme cases (how I would have loved it for The Grapes of Wrath in high school), but it’s up to you. On the Mac there are a couple options that I know of:
I don’t know the options for Windows as well, except for the cross-platform applications:
Please note these are not endorsements or recommendations, just pointers. If you have any suggestions, for either list, please send them to me!