SitePoint
MysqlConnectClass (good explanation of thinking the OOP way):
http://www.sitepoint.com/forums/showpost.php?p=683454&postcount=4
Advanced PHP Resources:
http://www.sitepoint.com/forums/showthread.php?t=78687
A web and systems development journal (from a–too busy–web developer who does a lot of various IT work.)