Stackable clear plastic totes (the HD style) have been a game changer for me. By grouping tools and supplies in them its easy to see what I have and find it when its needed. One has all my A/C tools in it; vacuum pump, oil, gauges, r-34, etc. Another has 12v electrical, another is household electrical and so on. Makes it easy to keep organized at a glance. I also use them to stage parts for upcoming projects; it keeps everything in one place so I don't end up with Jeep, car and motorcycle parts all spread out and unfindable.