Phishing security assessment tools allow you to identify knowledge gaps, the employees who are most likely to fall for scams, and the areas of your organization that are most susceptible to attack. Sophistication in this product space varies greatly, and free/open source tools are few. In the commercial space, often a phishing simulator and computer-based security awareness training are bundled together, so the wayward employee can be immediately "schooled".
Additional Reading and Resources:
How to Run Effective Phishing Assessment and Training Campaigns Employees Don’t Hate - InfoSecurity Magazine