The Social-Engineering Toolkit (SET) is a python-driven suite of custom tools which solely focuses on attacking the human element of penetration testing. It's main purpose is to augment and simulate social-engineering attacks and allow the tester to effectively test how a targeted attack may succeed. Currently SET has two main methods of attack, one is utilizing Metasploit payloads and Java-based attacks by setting up a malicious website that ultimately delivers your payload. The second method is through file-format bugs and e-mail phishing. The second method supports your own open-mail relay, a customized sendmail open-relay, or Gmail integration to deliver your payloads through e-mail. The goal of SET is to bring awareness to the often forgotten attack vector of social-engineering.
For download and more info check Social-Engineer.org
See also Malicious Email Social Engineer Attack using Social Engineers Toolkit (SET)