Ask HN: What are some important things to memorize?

[jpiasetz]

I've been trying spaced repetition and was curious what are some good things to always have at your fingers tips or know off the top of your head?

Ideas:

* Conversion metric to imperial * NATO phonetic alphabet * Powers of 2 * International Phonetic Alphabet

[VLM]

Theres a whole list here

http://mnemosyne-proj.org/card-sets