Jon Raasch's notes on Nicholas Zakas's Google Tech Talk "Speed Up Your JavaScript" in which he covers basic performance improvements like local variables for more expensive lookups, avoiding for in loops, casting DOM array-like objects into proper arrays, avoid touching the DOM, use classes to change CSS instead of inline styles.
Douglas Crockford discusses how to create private members and methods, and using privileged methods to bridge the gap between public and private. It also contains the simplest and most understandable definition of closures I've ever seen.