Visacast is one of the most interesting tools I've seen around for some time. It allows you to "split" an AAC file (alternative to MP3 for podcasts) to chapters. Each chapter has its own photo and URL link. iTunes allows you to jump to different sections in such a file and (I think) so does an iPod (photo or color?). Autoring is really easy, just drag'n'drop your photos, then set the time they will appear as you listen.
Awsome! I'll let you know how it works on iPod color as soon as I get mine :-)