Cory Hudson sees callbacks as benefiting from currying JavaScript functions, and defines currying as turning a function with two arguments into a function with one argument that returns a function of one argument. He starts off with two functions and shows how to combine them into one curried function, and also builds a generic version. He shows a good usage of a curried function in an array map() function, which is similar to Prototype's bind().
Erik Arvidsson warns against extending the JavaScript Object with Object.prototype, as it can lead to breakages in third party code when they use the for(key in obj) method of iterating through any class (since they all are subclasses of Object). Instead Erik recommends extending the classes that directly benefit from the extending functions, and treat Object as a final constant. Erik also suggests that hashes and associative arrays should be done in JavaScript using Object, not Arrays.
Douglas Crockford's useful utility that looks for potential problems in JavaScript code. Produces warnings like improper use of eval, and places where a dot operator is better than an array-like reference. An excellent tool to use before running JavaScript through a minifier. JSLint is actually a JavaScript parser written in JavaScript