EmailResponsibly: The Tangled Web of Email Segmentation

Segmentation is the key factor in ensuring you are engaging properly with your audience. This might be separate content for separate lists, auto pre-scheduled campaigns based on days since sign-up and triggers for activities or it would be who they are and what they do etc.
Don't forget, you've also got dynamic content to ensure that each individual in each category gets the right content too!

A three parter here from Jordon Lane for Email Responsibly for cover it for the most part!
Aug-07-2009: Part I - Behavioral segmentation
Aug-12-2009: Part II – Demographic segmentation
Aug-14-2009: Part III – Segment by acquisition channel