OWASP zap is one of the OWASP project. It is a penetration testing tool for web applications having similar features of Burp Suite. It has automated scanner to discover the vulnerabilities in application. Additional feature include spider for Ajax based application. OWASP zap can be used as a intercepting proxy also. OWASP zap can be downloaded from http://www.owasp.org/index.php/OWASP_Zed_Attack_Proxy_Project#tab=Main