This is for chili in a slow cooker and I'll be using red beans of some kind--kidney I suppose. I know I need to soak them, but do they need to be pre-cooked too?
As "Mrs Garden" states, the canned beans are soaked and fully cooked in advance.
Different beans (legumes) require different amounts of soaking and cooking, so you need to be specific as to the type in your decisions. Butter beans (lima) take very little time, Chick Peas (garbanzo) take hours.
Some legumes, like lentils, often do not need soaking at all.
Your example of red kidney beans are a special case, as they are toxic if not vigorously boiled for ten minutes before the cooking process to destroy the toxins in the skin. Note that cooking them under 100C actually increases the toxicity levels - poisoning from them is particularly noted with slow cookers.
Remember that the canned beans are designed to throw straight in to a recipe at the end, or the beginning, or be eaten cold in salads, they are fully cooked. If your recipe is going to cook for a few hours in liquid, then you may not need to pre-cook the beans, only soak them - as the cooking process will suffice. Take note that if the recipe is high in salt, it is not a good idea, as salt early in the cooking process hardens beans. A lot of slow cooker recipes can just have soaked and partly cooked beans added to them from the start.
My father never cooks red kidney beans before adding them to a chilli, just boils them hard for ten minutes to sort out the toxicity issue and throws them in for the full cooking time.
Dried beans, like other dried grains (barley, bulgur wheat, etc), should soak overnight with about 2.5 times as much liquid to dried beans. For example, soak 1 cup of beans in 2.5 cups of water over night. You can always drain the water that doesn't soak up. What I like to do is use hot water to cover the beans and the place plastic wrap (or a cover) over the bowl.
There are a couple of issues with using plain dried beans in a chili: 1. the beans won't cook at all, 2. the chili will take a really long time to cook, and 3. since the beans are soaking up all the moisture from the rest of your chili, the chili could become dry and sticky (think a can of Hormel chili that sat out all night).
If you have a pressure cooker, you can do a "quick soak" of the dried beans. I don't have the exact procedure/measurements close at hand, but here's the general idea: You put the beans and plenty of water in the cooker, boil them a short time at high pressure, then release the pressure quickly.
This has most of the same effects as soaking overnight in a fraction of the time. The downside is that it can be hard on the bean skins and some will rupture and/or come off. But all you've got is dry beans and you don't have all night to wait for a soak, this can get you to a cookable state very quickly.
Of course, this still leaves you with uncooked beans, but that's remedied by cooking your soup (or whatever) longer with a little more liquid than is called for with canned beans. Since you're looking at a long-cooking crockpot chili here, I don't think you'd have much trouble.