This idea incorporates some of this idea of package relationships: http://community.linuxmint.com/idea/view/1258
When browsing the packages either in the Software Manager or in the software section of the community site, in the various categories one often runs into applications, libraries, and plug-ins of various types. For a more clear understanding of what programs are available, it might be best to sort the libraries and plug-ins into separate sub-categories, so that the applications are highlighted and easy to find. Likewise, libraries would be easy to locate among packages, along with plug-ins, if given their own sub-categories.
Furthermore, there are some categories that might be able to use sub-categorization where none is currently present, for instance, the Office programs.
One possible method of accomplishing this could be tagging software packages with very simple descriptions of what kind of software it is, be it a library, plug-in (and if so to what program), a spreadsheet program, a text editor, etc. I don't see tags having any actual visual change in the software manager, only the community website, where information for creating sub-categories is done by analyzing the tags: the number of tags of a certain particular tag would be evaluated, and if a sufficient amount, the packages would be moved to their own sub-category.