Hi Bryan,
Within the Excel Add-in, you are not able to pull a one-to-many relationship, only a one-to-one lookup, in query. For example, within a task query, for example, you can pull the project's name, the project manager's name, and the project manager's direct manager. All of these are one-to-one lookup relationships. Since there may be multiple resources assigned to a single task, this constitutes a one (task) to many (resources) relationship. You can pull this information into the Excel Add-in by using the Resource Link query. See a screenshot here: http://screencast.com/t/fF8jyPom
More information about the Clarizen Data Model and relationships can be found here: http://usermanual.clarizen.com/#clarizen-data-model