Most toothpastes contain chalk as a whitener and abrasive to clean your teeth. The calcium in chalk is a very potent drawing agent, literally dragging the poisons out of the skin. Magnesium also works well, but is slightly harder to find. Mud works by drawing out the poisons through the skin as well it contains clay which is also a very potent drawing agent, as is charcoal from the camp fire. Charcoal helps with upset stomachs (after eating something you shouldn't have!)
I have used baking soda and water, and for some other stings which that doesn't work on, vinegar can help.
Plantain is a common weed which when chewed up and put on the sting often helps take the swelling down. It can also stain your clothes a lovely green. <img src="/images/graemlins/grin.gif" alt="" />
Now whenever I get a bite or sting I just give it a nice shock from a lawn mower, electric fence, etc. It is the best thing I have found to take the swelling down and limit anaphalaxis. <img src="/images/graemlins/shocked.gif" alt="" /> <img src="/images/graemlins/grin.gif" alt="" />
I have yet to find a way to fit the lawn mower into my FAK though! <img src="/images/graemlins/confused.gif" alt="" />