Basic Behavioral Targeting (and Segmentation) - BTBuckets
Behavioral segmentation usually catches the attention of privacy advocates but in the end, consumers spend and interact more when that functionality is present. As such, some level of behavioral segmentation is almost required these days if you hope not to fall too far behind.
Fortunately, there are some relatively easy ways to get started without breaking the bank - BTBuckets is one. The free web-segmentation tool allows sites to create user "clusters" based on user behavior. These clusters can then be integrated with your advertising server, content management system, web analytics (a tutorial for integrating BTbuckets into Google Analytics here) or any other site tool to ultimately create a richer user experience.
BTBuckets has essentially created an open configuration interface to allow for segment creation based on a combination of any interactions on your site. The service enables marketers to determine how much time users' must have spent before being added to a cluster, define how many times a view must visit content before being added to a bucket, and determine how long users will be kept in each cluster.
Overall, a very powerful service and one to consider. BTBuckets is free (it's in beta) but there is a five million monthly cap for each site. You should be aware that BTBuckets uses first-party cookies to control behavioral segments, but they have created an opt-out program for end users.