Normally this whole process of creating the PRN file is transparent, you print a document in your favourite application and the paper starts feeding through the printer. There can however be some uses for intercepting and capturing a PRN file before it gets to the printer.
(Lego) Brick Inventory DB. With this application, the user will be able to inventory his / her lego set collection, and build an inventory of the parts in those sets. Main goal of the project is to enable data exchange between different inventorying efforts, essentially connecting those isles together.
Find a base. Get a LEGO table or one of those green LEGO platforms. This will be the floor of your house, as well as the yard, if you save room for one. If you build your house in two parts, on two different platforms, you can open it up to see what's inside by pulling the platforms apart.