Bugcrowd allows you to tap the expertise of many professionals to root out vulnerabilities in your work. I find this invaluable, as having developers security check their own code is prone to error. I find it to be a great way to discover problems rapidly and allow my teams to work on what they're good at. Review collected by and hosted on G2.com.

While highly effective, the service can be expensive, especially for small, internally-facing code. For a higher level project, it's worth it, though. Review collected by and hosted on G2.com.