When you download a file off of audible.com, there is the capability of resuming where you left off once you exit listening to an audio book. Podcasts through iTunes do the same things as well. However, you may have an audiobook that is not through audible.com. The good news is that there is an Apple Script for that: Make Bookmarkable. This script will convert the AAC file extension in itunes to m4b format, which is recognized as the bookmarkable file. In addition, if you have iTunes 7 or greater, you can have the audiobook sound files automatically added to the audio book cateogry.