Much of the Pliny project work involved building software to demonstrate and explore the basic ideas behind the project itself: what aspects of humanities scholarship could benefit from computing support? Thus, a few screen shots will give some idea of what Pliny was about.
First, during the early phases of the project Pliny was one of the first pieces of work to demonstrate how digital annotation, focusing on how annotation was currently being done in traditional scholarship and could usefully be represented digitally. Here one can see Pliny being used to annotate an image -- in this case the frontispiece of Giambattista Vico's New Science. Pliny "out of the box" also supported the digital annotation of web pages and PDF files, and provided support for notetaking of non-digital objects like printed books.

More information about the early focus on annotation and notetaking and how, from Pliny's perspective, these digital acts could fit with the broader work of digital scholarship can be found in Bradley 2006, 2008 and 2008a.
As a part of the Pliny project, there was some thought put into considering what digital annotation of this kind was for. How did it support subsequent scholarly research work? As a consequence, Pliny contained mechanisms that enabled its user to fit annotations into an evolving interpretative structure. Here is an example of the kind of thing Pliny could support: the structures here assisted the user in sorting out a perspective on the uses to which 2D space was put in research:

The connection between Pliny and scholarly interpretation continued throughout the project. See an early discussion in Bradley 2008 (or the preprint), and some later ideas, centered on interpretation as process, in Bradley and Pasin 2017.
A little later in the project the focus shifted to how the ideas about scholarship support that were a part of Pliny could usefully fit with other digital tools and media beyond just basic webpages, digital images and PDF files. Demonstration tools were built for Pliny annotation of Google Maps, for the Victoria and Albert Museum's collection API, and (shown here) Northwestern University's WordHoard software:

Thoughts about how Pliny demonstrated a useful way to think about tool integration in the context of annotation and scholarly research can be found at Bradley 2007, Bradley 2008b, Bradley and Hill 2011 and Bradley 2012.
Later work on the Pliny project explored how Semantic Web technologies might apply to Pliny's representation of an understanding of scholarship in the humanities. Pliny tools were created not only to support the expression of Pliny material into RDF, but also to explore how Semantic Web sites like triple stores could, themselves, be made into objects for scholarly thinking and annotation:

More can be seen about this at Bradley and Pasin 2012 and 2017.
The Pliny project developed a plausible model of how a digital form of traditional scholarly annotation could be integrated into a unified environment that would support a range of humanities research aspects: including developing ideas, and writing about them. The most recent work in the project involves working to enhance the support for scholarly writing: developing a prototype platform which would help a Pliny user draw on material stored in Pliny to write an article. A screen shot for this prototype tool is shown here:

There have been no publications as of yet about this aspect of the work, but some early thinking about scholarly writing and Pliny can be found at Bradley 2009.