ExperimenTrak
   Provides online subject pool management. Includes a list of features.
   http://experimentrak.com/

Experimetrix
   Provides online subject pool management. Includes a list of features, a demo site, pricing, and customer testimonials.
   http://www.experimetrix.com/index.htm

Human Participation in Research
   Provides online subject pool management. Includes a list of features, pricing, and a demo site.
   http://hpr.msu.edu

Sona Systems
   Provides online subject pool management. Includes a list of features and customer testimonials.
   http://www.sona-systems.com