Thru-hiking the AT right now and I've found baking soda to become quite the multi-use item.
Stored in a snack-size ziploc bag, I brought along a few ounces.
Its uses:
-Toothpaste (I wet my toothbrush, dip it in to coat it, and brush away. Also a good mouthwash)
-Relieving heartburn (~1/2 or 1 tsp. with water and *poof* no more heartburn!)
-Stings/Bites (can be used as a scrub with water to remove poison oak, ivy, sumac oils and to heal. Also for insect stings/bites, put a little bit directly on the sting/bite and mix with a few drops of water to make a paste. You can cover with wrap or gauze and tape if you're on the go, or leave uncovered if you're lounging around.)
Definitely worth carrying around for me so far. :)

