LowPro is a scripting extension to Prototype written by Dan Webb to make unobtrusive DOM Scripting much easier. Included are an onReady event, adding behaviour using CSS selectors, fixing the this reference to always refer to the element within events, and a mechanism for triggering events.
Dean Edwards counters Dojo's Alex Russell's hideous hacks with two standards friendly approaches. Looking at the The DOM Content loaded problem and the sluggishness of walking a DOM Tree, Dean talks about speed improvements, including the use of XPaths.