[quant18]

There's insane amounts of great stuff hidden in the various nooks and crannies of the NIST website. Some of my other favorites:

Engineering Statistics Handbook http://www.itl.nist.gov/div898/handbook/index.htm

Digital Library of Mathematical Functions http://dlmf.nist.gov/

The Quantum Algorithm Zoo http://math.nist.gov/quantum/zoo/

[onan_barbarian]

Agreed on the Engineering Statistics Handbook, especially Section 5 on Process Improvement, which contains a decent (and free) treatment of Design of Experiments. A lot of the earlier sections are ok but not as sharply interesting, but their DoE stuff is quite good.

[Entaroadun]

I was just reading this section yesterday!