http://www.buzzmath.com/
BuzzMath is an interactive math workbook that has more than 2700 online math problems with instant feedback and step-by-step solutions. Teachers can use it to generate assignments, demonstrate problems on the SMART Board, produce random math problems, and generate achievement reports to determine areas of need. Parents can use it to provide additional math practice to increase understanding in problem areas. Students can use it to solve math puzzles and enigmas, play games, and additional study and practice. BuzzMath is free to use but also has a subscription-based program with enhanced features. As of September 1, 2011, one teacher at every school will be eligible for a free subscription to BuzzMath!