Heidi Cohen of Riverside Marketing Strategies recently published a great primer on some of the techniques you can use to target your emails more effectively. In her article over at Clickz.com, she does a great job of introducing "behavior based email marketing" from a relevance (i.e. past products purchased) and lifecycle perspective. Take a read - Behaviorally Targeted E-mail Communications, Part 1.
Another great primer can be found at emailuniverse. There Christopher McKnight provides Segmentation 101. If you are just starting to think about targeting your emails based on behavior. Or, better yet, you reviewed your Top Right customer behavior based dashboard and are in brainstorming mode, it's a good place to start.