New Scientist has an article about Claytronics, also called programmable matter or Synthetic Reality. From what I understand, it's essentially nanodust which can programmatically be "molded" into three dimensional objects. Very cool and more than a little scary. The NS article suggests using it as a kind of remote representation of one's self (think of a very realistic conference call), but I can think of dozens, hundreds, thousands of other possibilities, not all of which are warm and fuzzy.