Mark,
You may want to search for a similar thread from a couple of months ago. I use a hydration backpack and carry water, power bars or trail mix, wallet and sometimes my cell. I carry a small tool kit, spark plugs, plug wrench, Co2 cartridges, first aid pak and a shop rag in the rear fender bag. But, I'm lucky to ride with an "Eagle Scout / McGuyver" type buddy of mine who wears a large hydration backpack with multiple pockets holding almost anything you can imagine from duct tape to tp. His bike is also equipped with a GPS and we carry maps for back-up. His enclosed trailer is equally prepared and I just add my toolbox. In there we've got spray cleaners & lubes, spare air filters and filterskins, tubes and patch kits, bike stands, small air compressor. Anything more involved than that and our day is most likely done.
Good luck and enjoy the trails.