I was surprised when my husband suggested I pour some ammonia on my foot when I was stung repeatedly by a scorpion. I've been stung before and just suffered from it for days. The ammonia took the sting out immediately. This also works on bee stings or any other kind of insect sting. Cheap enough!
Witch Hazel also works well.
When I was a teenager and babysitting a little, I happened to be skimming a Dr. Spock book while at a job. Spock recommends this for insect bites and just after reading this, one of the boys I was watching was stung by a hornet. He was running around screaming (very dramatic child) and I came out with the ol' Witch Hazel and he finally quieted down. His mother told me that, the next day, he didn't even have a red spot!
Must be some sort of "drawing out" factor in the ammonia and Witch Hazel...whatever it is, it's a good thing because they're cheap and work well!