An app that allows you to categorize your written content, whether it is exists on the web, is a pdf, an ebook, or plain text.
It is currently a work in progress, and will probably be a long time in the making as I'm using this as both my first serious Coccoa application. I think the problem domain is simple its just a matter of bringing a slick UI, and flexbility to the platform. This will be open source and free unlike the many other alternatives to storing files. I really want a good way to organize my massive pdf reading list, and that is the primary motivation, because most ways suck, or have non-intutive interfaces. I'm thinking Sparrow for PDFs.