I use the small Steri-Lite 3 drawer units.
http://www.bing.com/shopping/sterili...awer&FORM=HURE They will stack 3 high and are tall enough for thread spools and king cones. I have 4 units now and wish I had room for more. I have 2 of the 3 drawer rolling carts under my counter for serger cone thread, larger items like stabilizer rolls and some yarn and knitting stuff I will NEVER use, but can't find anyone to pawn it off on.