Ivo Wetzel covers some of the quirks of the JavaScript language. Some of these cause subtle bugs, some overturn conventional wisdom. It covers toString on numbers. Covers the advanced JavaScript features such as prototypal inheritance, this, closures, anonymous wrappers, type-casting, automatic semicolon insertion and hoisting of function and variable declarations.
John Resig explains JavaScript timers. Because of JavaScript's single-thread nature it is easy to write blocking code that makes pages unresponsive. Timers allow us a mechanism for yielding control back to the browser, queueing the code up to run a little later. John goes into depth on this particular topic.