kot (rubygems):   Kot is a basic toolkit for getting started with computerised adaptive testing (CAT). It includes a module to calculate item response theory (IRT) statistics for dichotomous items with 1-4PL characteristic curves (ICCs), a Hill Climbing ability (theta) estimator, a Randomesque selector and a Test class to make tying all this together easier. 
Keywords: computerized-adaptive-testing|irt|item-response-theory|psychometrics