For those wondering where to get willow bark, it's really pretty simple. Cut yourself a couple of willow switches (watch the neighbor kids run for the hills (/joke)). If you don't know what a willow tree looks like, google is your friend. Scrape off the outer bark carefully, leaving the spongy inner bark. Strip the inner bark and save it. You can either use it right away or dry it out and put it in sealable jars.
What is willow bark good for? Anything aspirin can do, willow can do better, and usually without the side effects. I like using it with spearmint, lemon and honey for a nice winter throat balm that helps with colds or flu symptoms. About a tablespoon willow bark, teaspoon lemon juice, tablespoon spearmint and tablespoon honey in hot water makes about a quart of throat balm.
I've also used willow bark to help with inflammation on wounds in a poultice. If you mix it up/grind it with plantain leaves and place it directly on the wound, you can then wrap a bandage (if you don't have any, use an undamaged plantain leaf to cover the poultice) over it and it will help cool the wound, take a lot of the pain away and prevent infection. Some people say to chew the leaves, but I would remind them that there is more bacteria in your mouth than on the leaves normally and spitting in a wound is not a very good idea. A little clean water is better, iodine is best. Iodine does amazing things, from cleansing bacteria to curing cancer, prevents infections, and your body needs it, badly. (today's diets do not contain enough iodine, even with iodized salt...)