I have more stash than the WM I work at does!
about 90% of my stash was bought/obtained before learning how to knit. I have at least a dozen of the LARGE rubbermaid bins that are labelled with the type of yarn or thread in them. I have over a dozen of the smaller ones for my smaller balls of thread and for WIPs/UFOs. These all stack together {relatively} neatly, and having labels on them makes it easier when I'm looking for something in particular. I also have several large garbage bags of yarn... 2 have the pounders of RH Comfort I pick up at work, 2 more have a bunch of small balls of Eaton's sayelle I got at a garage sale 2 years ago. I also have 2 tubs with a hole in the top of the lid that I use for current projects by my computer, and a rolling drawer thingy with three drawers... bottom drawer has leftover yarn balled up, middle has sock yarn, top has my "finishing" tools.
I've got tons more elsewhere in the house, but I don't have enough bins for it all, and it's too cold to go into my yarn cryogenics testing lab/craft room right now and organize it better. It's actually our front porch {closed in}, but it's not insulated, so I spend about a month every spring "fixing" the damage I did over the winter with quick dash and dumps!