Helpful sites

A site that has some helpful information about PHP and MySQL coding, although i would only recommend it for beginners as some of the code is a little bit basic.

http://www.php-mysql-tutorial.com/index.php

A guide that tells you how to create an RSS feed, really quite simple.
http://searchenginewatch.com/showPage.html?page=2175271

An RSS feed validator that checks your code for you. Very helpful
http://feedvalidator.org/