outlines common web app security vulnerabilities

don't use these passwords ... or anything like them. and if you're trying to hack someone else's account, try these first :)

google U's web security tutorial. set up a pseudo-private instance of a web app and learn to exploit it.

a ton of common [categorized] C code-isms that are insecure or unstable. definitely worth looking at if you code in C ... or C++ ... but there's an additional guide for C++

Self Assessment Questionare for PCI compliance.

PDF outlining PCI compliance guidelines.

security articles and software

archived articles from various security mailing lists

concise document outlining general PHP/webdev security concerns

some of the javascript required to implement field-level security.