OpenSAML is a portable implementation of the Security Assertion Markup Language (SAML) standard for the formation and exchange of authentication, attribute, and authorization data using XML, as defined by OASIS. There are interfaces for a range of languages, including C++ and Java.
ratproxy is a semi-automated, largely passive Web application security audit tool optimized for accurate and sensitive detection, and automatic annotation, of potential problems and security-relevant design patterns based on the observation of existing, user-initiated traffic in complex Web 2.0 environments.
skipfish is a high-performance, easy, and sophisticated Web application security testing tool. It features a single-threaded multiplexing HTTP stack, heuristic detection of obscure Web frameworks, and advanced, differential security checks capable of detecting blind injection vulnerabilities, stored XSS, and so forth.