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.
Christian Heilmann lays out seven rules to better unobtrusive JavaScript, including not making assumptions about JavaScript, the browser and the document. Work with structured markup. If you are traversing a document, maybe there's a solution that can take advantage of CSS's selector mechanism instead. Work with browsers and users. Better understanding of events, and playing nice with namespace, scope, and patterns. And of course, think about the next developer, so keep the code maintainable.
Simon Willison blogs about how JQuery won him over. From its faddish start based around CSS selectors (getElementsBySelector), and method chaining, Simon now sees the library in a new light. Simon shows how jQuery supports modern development best practice such as namespaces, giving a quick nod to the richness of jQuery selectors (DOM, CSS and XPath). JQuery's event handling looks natural and offers an event when the dom is ready. It exposes custom events for non-trivial Ajax requests. Simon's so convinced about jQuery that he's willing to overlook his rule that developers should know how a library works before using it.
A DHTML shell that allows you to query the current browser window. Includes command line JavaScript execution, mouseover DOM query, CSS input, tab completion, profiler and object inspection. Can be configured to run off a bookmarklet, and works in IE, Firefox, Safari and Opera