Filing cabinets are a dime a dozen at yard sales. Verticals, horizontals, etc. The two and four drawer horizontals make very good large tools storage units. I have a two drawer that I put a Craftsman Top Box on and it is very handy. All of my drills, drill bits, drivers and battery charging stuff is in this cabinet.
I also use a file card unit for nut and bolt storage.
Regular vertical files make great part and tool organizers. Here are two I put on casters. Putting the cabinets on casters makes it easy to clean and re-organize.
And don't forget old kitchen or bathroom vanities.
I trash picked this one, rebuilt it, painted it, added the 2 x 6 raiser and threw on a steel top. Cost me 40 bucks total...
Mark