Although not typical, it is an occasional necessity to store sensitive data in a website in such a way that it is reasonably well protected from prying eyes. On a recent project, we needed to implement a method for content editors to encrypt some parts of the nodes' content.
Views is an essential part of any Drupal site. It is very versatile and allows non-developers to set up all kinds of listings of their content. However, no matter how versatile it is, you will always find a scenario that is not feasible to set up on its user interface. But if you are a developer, you have even more ways of manipulating views.
When setting up content types on a more involved site, a developer could easily end up with having an enormous list of fields in one single content type. When this happens, I tend to pause for a second, and think through whether there is any way to consolidate that list. Chances are, I find a field or two whose values either depend on other fields or can be generated without user input. These are the exact scenarios where the Computed Field module can be a great choice.
Although the CCK3 module had never seen a full release, it was still worth upgrading Drupal 6 sites from CCK2 to CCK3, because the latter added a very compelling tool to CCK's arsenal: Multigroups. This feature allowed users to group several fields together, and enter multiple values into that set of fields as a whole by repeating the field group whenever a new value is added.