Folklore facts on probability distribution learning, testing, and whatever-ing

A comprehensive 10-page probability cheatsheet that covers a semester's worth of introduction to probability.

📙 The probability and statistics cookbook

Probability and Statistics: a simulation-based introduction. An open-access book.

IPSUR, Introduction to Probability and Statistics Using R, is a textbook written for an undergraduate course in probability and statistics. IPSUR is FREE, in the GNU sense of the word.