This is a partial list of things used in making soap. Those marked with an * are suggested as the required minimum. Like any hobby, the list will get longer - it always does.
* Lye. Sodium Hydroxide, NaOH, for bar soap; Potassium Hydroxide, KOH, for liquid soap.
* Carrier oils and fats (Coconut oil, Crisco, olive oil, shea butter, etc.)
* Distilled water. (Available at most supermarkets)
* Stainless steel (or enamel) stockpot(s) (4 to 30 qt. depending on size of your recipe). For safety, oil plus lye solution should be less than ½ the pot height.
* Large stainless steel spoon for stirring.
* Stick Blender.
* Lye mixing container (2 qt. vinyl drink container will work quite well).
* Soap molds. Can be homemade from PVC pipe or wood. If using wood molds, you'll need freezer paper to line the mold. There are many styles of wood and silicone soap molds available for sale on the internet.
* Thermometer (a candy thermometer will work).
* An accurate weighing scale. Kitchen scales adequate for the beginner can be found online for 15 to 30+ dollars. One that displays ounces/lbs/grams and measures in graduations of .01 to .1 oz and 1 gram would be preferable. It's important to get a scale where the display can be read when your soap making pot is on the scale.
* Running water & vinegar to neutralize small minor lye splashes.
Vinegar is used for small drop splashes on the skin. The vinegar is used only after flushing the area very well with water. That removes the large majority of lye. Then vinegar will neutralize the small amount of lye left on the skin. If lye burn is more extensive or in the eyes - call 911, while rinsing with water if possible, and keep rinsing with water until someone arrives.
* Goggles or some form of eye protection.
Medium to large rubber spatula to help empty soap into molds.
Stainless steel spatula to scrape sides of pot (for DBHP hot process).
Essential oils and/or Fragrance oils. (Warning, collecting these can be addicting.)
Coloring agents. (Ditto)
A few things that were probably left off the list.