For my own reference and for anyone happy to benefit from my bookmarking, here are some sites I’ve found useful during novel research:
Affect vs. Effect – because looking it up every time is easier than memorizing them both.
BLM General Land Office Records – for the punctilious author of American historical fiction, when historic land description is called for.
Mining Job Title & Descriptions – a nice guide to who-does-what in the mining industry.
Pit Terminology – offers an extensive list of terms specific to mining.
Surname Search – by country, very handy.