I Know It is the excellent new (beta) site from Super Teacher Worksheets for interactive Math lessons grades K-5th. This is a super fun easy to use site for practice on a wide range of topics, such as: place value, multiplication, counting coins, time, and more. Best of all, I Know It, allows a user to use a certain number of "hints" to help solve a problem and it gives the correct response w/ reason for the wrong answers.
I highly recommend checking out I Know It by clicking here!!!