This paper describes a deployed educational technology application: the CriterionSM Online Essay Evaluation Service, a web-based system that provides automated scoring and evaluation of student essays. Criterion has two complementary applications: E-rater®, an automated essay scoring system and Critique Writing Analysis Tools, a suite of programs that detect errors in grammar, usage, and mechanics, that identify discourse elements in the essay, and that recognize elements of undesirable style. These evaluation capabilities provide students with feedback that is specific to their writing in order to help them improve their writing skills. Both applications employ natural language processing and machine learning techniques. All of these capabilities outperform baseline algorithms, and some of the tools agree with human judges as often as two judges agree with each other.