What (not necessarily LW-related) things do people find useful to Anki? (Or have Ankied but they turned out not to be useful, etc.)
Some things I have:
the NATO phonetic alphabet
mass of Earth/Moon/Sun, radius of Earth/Moon
log_2 of 1.25, 1.5 and 1.75, and log_10 of 2 through 9
The 68-95-99.7 rule
Some things that I noticed I had to keep looking up: which is which between SQL left and right joins; the argument order to python's datetime.datetime.strptime function; the spellings of irrelevant and separate
I think only the latter group have had any use worth speaking of so far, though the third and fourth are things that I have more than once wanted to know and not known. The first two may just be almost-useless (though I like knowing them, so not necessarily worthless).
Things I kind of want to remember but suspect they wouldn't be worth it include other alphabets, and locations of countries/US states/UK counties/London underground stops (the aggregate may be useful, but there's an awful lot of cards there).
Some stuff I used Anki for: