From eEye Digital Security:
Retina Community is a completely free tool powered by eEye's renowned Retina Network Security Scanner technology. For up to 128 IPs, the product identifies vulnerabilities (including zero day), configuration issues, and missing patches across operating systems, applications, devices, and virtual environments.
Free but Feature-Rich: * Vulnerability assessment for up to 128 IPs * Zero-day vulnerability identification * Identifies whether a vulnerability has an associated exploit from Core Impact, Metasploit, or Exploit-db.com. * Right-click Metasploit (3.6.0 or higher) integration. * SCAP configuration scanning * Integrated vulnerability updates and alerting * Detailed vulnerability and executive-level reporting * Report export to XML, CSV, and PDF * Online support and resources from eEye's research team