1. A computer-implemented method of assessing spontaneous speech pronunciation, comprising: performing speech recognition on digitized speech using a non-native acoustic model trained with non-native speech using a processing system to generate word hypotheses for the digitized speech; performing time alignment between the digitized speech and the word hypotheses utilizing a reference acoustic model trained with native-quality speech to associate word hypotheses with corresponding sounds of the digitized speech; calculating statistics regarding individual words and phonemes of the word hypotheses using the processing system based on said alignment; calculating a plurality of features for use in assessing pronunciation of the digitized speech based on the statistics using the processing system; calculating an assessment score based on one or more of the calculated features; and storing the assessment score in a computer-readable memory.