Following are some links that may help your exploration of testing along:

The Performance Testing Council

This is a group of test developers dedicated to understanding performance testing theory and practice.

http://www.PerformanceTest.org

The Association of Test Publishers

This association of testing vendors is a great forum for keeping up on developments in multiple-choice testing.

http://www.TestPublishers.org

Item Response Theory – Larry Rudner

The entire site is a treasure trove of instructional materials about Item Response Theory, and testing in general.  Excellent.  Accessible.

http://www.EdRes.org/IRT