The New Yorker has an interesting short article on how the names of the dead will be arranged at the 9/11 memorial (due to open on 9/11/11). It's a solution to a problem that I'd not thought of: when you have several places to display names, which names go in which place, and what order do they go in? I'd most likely have opted for a simple alphabetical order, but as the article points out, this is actually less than ideal.
The solution turns out to be mathematically challenging, and computers were used to figure out the final ordering. The guiding principle used is “meaningful adjacencies”, meaning that names found next to one another are connected in some way (organizational affiliation, relationships, families, etc.). Fascinating stuff.