Try the American Red Cross for first aid classes. What they give you is the type where 911 is right around the corner, but it's good for a start, and at least teaches you the general principles of the initial approach, triage, how to do CPR and to stabilize things for the short term. The Red Cross occasionally offers backcountry or wilderness first aid courses. NOLS offers them around the country. These are generally 16-hour courses taking place over 2 days and generally cost about $200. You can find out the nearest ones by googling. If nothing else, at least try to get the simple 4-hour course offered at most workplaces. My church offered one for free last spring. It wasn't comprehensive but was an excellent review for me and was certainly excellent for those who had never had first aid.

One thing a good first aid course will teach you is how to improvise things like splints and such from what you have rather than taking an extensive (and heavy!) first aid kit that you'll probably never use. Of course if you're going with a party and are responsible for the group first-aid kit, you'll need more--but if this happens you'll also need the training.

My kit is mostly bandaids, moleskin, "Second Skin," a few non-stick gauze pads, two one-time packs of antibiotic ointment, one or two sanitary napkins (which per my first aid instructor make the best compresses for heavy bleeding), a few pills--lotromin, benadryl, tylenol. For my dog I take buffered aspirin, an extra-large size doggie boot to cover a bandaged pad, and self-adhering veterinary wrap, which (with a little duct tape reinforcement on the outside) works fine for human sprains, too. All the rest of my stuff (except tylenol, which is poisonous for dogs) can be used on either me or the dog. As you may notice, my kit ia pretty heavily slanted towards blisters and minor cuts. I also have a couple of clean empty ziplock sandwich bags in there to use for wound irrigation (put tiny hole in one corner of bag and squeeze).

Be sure your kit includes any medications you personally need to take. Label them well. Any narcotics should have the prescription label on them and should never be given to anyone else.

Re first aid books and internet information (the latter is often not dated--never use undated information): If they mention tourniquets for anything (except an already amputated limb), or snake bite treatment consisting of cut-and-suck, venous tourniquets or Sawyer extractors, they are woefully out of date and should not be used. This per my-son-in-law-the-ER-physician. CPR has also changed (since my prior course in 1998)--it's now 2 ventilations to each 30 compressions.