Security (php,MySQL and more)
" Founded in January 2005, the PHP Security Consortium (PHPSC) is an international group of PHP experts dedicated to promoting secure programming practices within the PHP community. Members of the PHPSC seek to educate PHP developers about security through a variety of resources, including documentation, tools, and standards. In addition to their educational efforts, the PHPSC engages in exploratory and experimental research in order to develop and promote standards of best practice for PHP application development "
Tech Tips is "a collection of tips on a very wide-ranging list of topics", digitalparadox is about all kinds of security problems, securityfocus is "the most comprehensive and trusted source of security information on the Internet", hackerscenter "group is aimed at researching into web applications security field".