An example of this can be seen on Squidoo, a web 2.0 site. An older series of lenses included 6 species of American salmon. Next in the series was a lens for Arctic char, a related fish:

More recently, lenses were added for several North American freshwater trout:

brook trout
brown trout
lake trout
rainbow trout

During the research the process,  several other species  were noted that may warrant additional pages.

To compliment this content one or more categories of T shirts, stickers and other artwork were created for each species, some of which can be displayed on pages where content exists related to each species.

An example of  this can be seen in this  section for rainbow trout artwork.

More examples of products create to accompany content can be seen in this category of fish art.

Promoting content is also easier as a group. The technique allows creation of articles that provide important backlinks to several pages at once.

Examples of this can be seen in these articles:

Trout and Char of North America

Trout and Char Art