A slip-box is really just this: a loose collection of slips stuffed into a box. Each time you have an idea that seems worth remembering you scribble down a note on an (electronic) slip and put it into the box. Then you can forget about it. When the time comes that you need your ideas, the functionality of the program helps you to quickly find relevant slips and, what is more, relations and links between different slips by associative searches.
The SlipBox application provides a plug-in architecture to establish interfaces to other programs, eg to BibDesk, Bookends (programs to manage references), Skim (a PDF reader and annotation tool) and Graphviz (a graph visualisation tool).