I discovered Bathsheba Grossman's stuff about 5 years ago... amazing 'mathematical' sculptures. My favourites, though, are the accurate 3-d crystal models of the galaxy, large scale structure of the universe etc-. These are great for contemplating either your cosmological insignificance or the awe-inspiring majesty of the universe you find yourself breathing in-and-out in. (depending on your exact level of optipessimism). I think i'm going to buy a few.