What type of flour should I feed my starter with? Different sites recommend different flours for the feeding of my established starter, so I suspect it depends on the purpose, but I can't find a definitive answer. Should I be using the  flour I plan to bake with next? Will mixing and matching make a difference? Do certain types produce more activity? Better flavor?
Once my starter was established (started with organic whole wheat flour) I've been feeding it with unbleached AP flour (King Arthur) and that's worked fine. I do this simply because it's the flour I buy in large quantities to stock my pantry, and so it's generally the cheapest flour I have on hand.

If you want to "switch over" to a different flour you can always scoop out a bit of starter a couple days before you bake, and feed it with the different flour. Start with a small amount so you don't have to throw any away; just double the volume with each feeding. I don't usually bother, though.