The list of categories that have been put forth so far have great suggestions but I feel like there's a more elegant way to lay it out. PBTA and FITD are popular but there are a lot of people designing for Fate, D&D, and other popular systems too. A general "Hacks" category feels inadequate to fit all of those, but individual sections for every game would be a cluttered mess. I'm not sure what the answer is.