Over on RPGNet, someone suggested creating an "Optional Rules Tracker" for GURPS - a sheet of some kind where you could list which optional rules are used for your campaign.
Such a tracker would be fairly easy to do as a Google Sheet, but I think it would be a good idea to create an index page for optional rules. However, I don't have a clear idea yet on how to organize an "Optional Rules" index - any suggestions? What are the possible categories and subcategories?