CCK

since CCK can dynamically alter the database schema (when you add a field to a second content type or change the number of values) the query may break.

Fortunately CCK provides functions for finding a field's table and column names so it's simple to do it correctly

Karen Stevenson showed me how to do this ages ago, but i think i documented it in code instead of online, so here's the link to Drewish explaining.

Shows what CCK columns get used in a view filter or relationship and give you the option to add an index on it so the views query will run faster. Also can add indexes to core modules.

The Node Relationships module provides methods to complete two way relationships between content types enhancing the features of node reference fields.

Backreference Module provides a nodeapi interface to maintain 1-1 relationships between all shared instances of a nodereference field. This means that given a field instance of field_reference1, if you add a reference to NodeBeta to NodeAlpha's field_reference1 and NodeBeta has an instance of field_reference1, then NodeAlpha will be added to NodeBeta's instance of field_reference1.

CCK Select Other introduces an alternative select list widget that provides a user with either a select list or text input.