Michael Cole has a revamped website, with an easy category navigation, a video and newspaper section, and a comprehensive archive. One article I would recommend is the "My Name is" Cipher Motivation, examining the driving force behind Zodiac's ego and his ability to respond to the newspaper articles that crossed his path. However, there are numerous extremely interesting articles and a comment section so you can contribute your thoughts. Here are five other articles from the website I would recommend to get you started.
1. PAUL STINE:A VICTIM OF OPPORTUNITY
2. CHARLIE CHAN AT TREASURE ISLAND
3. ROBERT DOMINGOS AND LINDA EDWARDS VIDEO
4. ZODIAC EXCEPTIONAL RELATIONSHIP SYNDROME
5. SAN DIEGO-RIVERSIDE CONNECTION?