Social-Engineer Toolkit is described as 'The Social-Engineer Toolkit is an open source penetration testing framework designed for social engineering. SET has a number of custom attack vectors that allow you to make a believable attack quickly'. There are more than 10 alternatives to Social-Engineer Toolkit for a variety of platforms, including Linux, Windows, Mac, Online / Web-based and BSD. The best alternative is Metasploit. It's not free, so if you're looking for a free alternative, you could try Censys or Armitage. Other great apps like Social-Engineer Toolkit are ZoomEye (Freemium), Exploit Pack (Free, Open Source), Cobalt Strike (Paid) and Nexpose (Paid).
Immunity's CANVAS makes available hundreds of exploits, an automated exploitation system, and a comprehensive, reliable exploit development framework to penetration testers and security professionals worldwide.