I saw a question in another blog (sorry, I neglected to write down which one) about pdfTeX's \pdfnormaldeviate primitive (also exists in MetaPost). Since I feel semi-responsible for the pdfTeX manual these days, I looked into the sources, talked to Thanh and Taco, refreshed my memory of normal distributions via wikipedia :), and came up with this:

\pdfnormaldeviate

Generate a normally-distributed random integer with a mean of~0 and standard deviation 65\,536. That is, about 68\% of the time, the result will be between $-65536$ and $65536$ (one standard deviation away from the mean). About 95\% of results will be within two standard deviations, and 99.7\% within three. This primitive expands to a list of tokens. \introduced{1.30.0}

Feel free to send me any questions/comments about this or other bits in the pdftex manual. Simplest to email me directly.