Once I found some of those clear acrylic boxes they used to make for storing shoes, clothes, etc. at a yard sale. I was delighted because the ones at Wal-Mart, Target, etc. are semitransparent and often have a blue or green tint to them.
And unfortunately, they don't seem to make the really clear, transparent ones any more as I've looked time and again.
The ones I found are large enough to hold 1/24 scale cars with room to spare and a 1/48 scale Mig-21. I place the model in the clear plastic box to keep the dust off them, the box goes on a bookcase or some other shelf and surrounded by common glass insulators from my insulator collection. A few insulators are placed on top of the box, too; they keep the cat from jumping onto the shelf or investigating the models too closely.