If your comic books are chaos, or your board game collection has gone out of control, GCstar might be the solution you need. GCstar is a free, open source collection management application for GNU/Linux systems.
When it comes to documentation, the GCstar site offers some in French, which makes sense considering the application’s creator is French. The GCstar site doesn’t have any English documentation yet, so if you’re looking for a fun way to contribute to an open source project, maybe this is the one for you.