Audiobook Builder
Audiobook Builder is one of the apps that I use about six times a year, but it's easily worth the $4.99 purchase price. It allows you to combine audio file, create chapter stops, and then end up with a .m4b audiobook file. This is especially helpful if you have a collection of lectures or seminars that you want to listen to. With an easy drag and drop interface, you can take dozens of audio files and send them to iTunes as a single file.