How do you use Categories in your task or calendar management?

[daddydave]

Since I don't see a "Getting Organized" section for 2010, and people are still posting in this section, I have to assume "of 2009" no longer applies. So here is my "getting organized" question.

This is a question for people who use tasks in any task managment software. Or, if you like, appointments or calendar items in any calendar software. Do you use categories (or tags) for your tasks and calendar items? If so, how do you use them? I am especially interested in non-GTD uses for categories, although use of categories by GTD users for purposes other than GTD contexts or GTD projects would also be interesting. This question is for any task or calendar management you use, RTM, Outlook, Toodledo, or what have you.

[Tuxman]

I use MiniTask as my task management, so "categories" are not really available, it is more like "headlines".

Tasks related to a (yet to finish) application I have been developing are put under the name of the application, I also have some "work", some "blog" and similar headlines. Well enough for me, currently having 23 tasks in there.