PhET Colorado Simulations is aimed towards college-level and high school earth science students and includes interactive simulations on many different earth science topics.
Regents Exam Prep has reviews, study-aids and problem sets in various earth science topics.
Classzone is aimed toward high school students and has good visualizations of various earth science topics.
HippoCampus is another simulation and video website on many earth science topics.
Earth Science Practice Quizzes on various subjects including the solar system, rocks, minerals, and plate tectonics.