PHP

put the following code in the beginning of php script to enable php displaying all php error

error_reporting(E_ALL);

RSS

RSS Java Library - Rome
Steps to publish your google blog via RSS
Steps to publish your google calendar via RSS (e.g. https://www.google.com/calendar/feeds/twhtanghk@gmail.com/public/basic?orderby=starttime&sortorder=descending)
URL to get RSS feed from google picasa photo album
URL to get HK weather with temperature in Celsius

Social Network

Comparison of Social Network Engine published by Wikipedia