One of the most underutilized defenses is information sharing with other organizations that face the same type of cyber threats. The financial community, through the FS-ISAC (Financial Services Information Sharing and Analysis Center), has a very good reputation for comprehensive and rapid exchange of information. There are many ways to share information and ultimately real time, machine to machine sharing through standard protocols will help alert many different types of organizations to new threats.
You can start with sharing inside your organization, and then carefully expand the number of trusted relationships. Your board of directors may have interlocking relationships with other companies and may be able to enable some valuable partners. Some cyber vendors have made a strong effort toward exchanging information. Mandiant® (part of FireEyeTM) offers a public domain version of their sharing structure called Open-IOC (Indicators of Compromise). Like many new initiatives, getting started is the hardest part.