I have a custom post type for birds that are available at my client's store. The post type has two related taxonomies called "Species" and "Breeds".
I then have several custom fields that can be set for each individual bird, the important one here is "Adoption Status". This field has three options: Available, Available Soon and Adopted.
When a bird has been adopted (purchased), rather than taking the bird off of the site (adopters are encouraged to join the community of our bird owners and removing the bird would take away our ability to link that bird to the new member's profile later) we want to be able to direct interested parties to birds of the same breed that ARE available.
So on the individual bird page, when the bird has been adopted, the status reads "[bird name] has been adopted". In addition to that I want to have something that say something like "We currently have [number of species available + number of species available soon] [species of current bird] that you may be interest in." and have that link to an archive page that shows only those birds of that species that are NOT adopted.
I can already link to the archive page for all of that species of bird, but it adds an extra step for those I want to direct to just those birds that they can adopt now or in the very near future. I could add a parametric search, and plan to have one in the sidebar) but I would really like to have this additional little bit of functionality.