Paul's examples

Short Examples:

SimpleXML
5-second Atom parser
REST
PHP 2 JS
JS 2 PHP (and back)
Ajax in 30 seconds
Ajax in 45 seconds
Ajax in 60 seconds
Javascript libraries to the rescue
Small changes, big rewards
Building up
Earthquakes!
GeoPlanet
HTML5 Geo
One API to rule them all
Geo bounding box for place names
Geo bounding box for place names with TABS!
YQL - Oath
BOSS
Lions and Tigers and Semantics, oh my!
SearchMonkey
Header for these examples

YUI Examples :

Simple dialog
Modal dialog
Tab view
Data table
Calendar
YQL

Long examples :

Wow Duel in PHP (source)
Wow Duel in Javascript + YQL (source) built up in stages
stdicon (appengine source)