Of course I can't go into too great of detail about what I've worked on because of NDAs and the like. However, I can show a couple of types of email I had worked on, based on the fact that they are in circulation.
Single New Product Mail
This mail features new products, and is targeted based on previous customer activity at Amazon. While I did not participate in the creation of the actual template, I did write the original automated processes which allowed the mails to be automatically generated.
This mail features products which have recently dropped in price, and is targeted based on previous customer activity at Amazon.
Email Opt Out System
The current incarnation of the opt-out system is about 10 months old now. Instead of doing direct database access, there is now a full Email Preference Service running which abstracts out the data.
Customer Information Cache
The core customer information system at Amazon absolutely cannot handle the load our team requires, so we built a system which refreshes all the pertinent customer data nightly from a data warehouse, and uses that instead.