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.
Three top features of jQuery: the multitude of selectors, manipulating attributes, and tacking Ajax/JSON requests. Choses jQuery over Prototype
As well as supporting CSS based selectors, jQuery also supports XPath expressions. This page lists a plethora of code snippets demonstrating jQuery's XPath matching capabilities.
A useful overview / introduction of the jQuery library, covering using selectors and XPath expressions to target specific elements in a document, simple Ajax requests, the basic animations available, restructuring a document, creating jQuery plugins.
Mark Pilgrim's essential online book about developing Greasemonkey scripts. Excellent starting point for Greasemonkey developers. Covers everything from setting up a Greasemonkey scripts to common DOM coding idioms, as well as a brief rundown of XPath, and case studies of Greasemonkey scripts.
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.