Thinking Blocks provides interactive templates in which students use brightly colored blocks to model and solve problems. As students work through the problems they are provided with feedback as to whether or not they are using the correct sequence to solve each problem. There are templates and problems for addition, multiplication, fractions, & ratios. You can also develop your own problems using the modeling tool.
You will need to familiarize yourself with this site first and then model and introduce it to students in order to get the most out of it, but it is a great way to prepare students for those TEI questions that they will see on the SOL test AND help them become more accustomed to more rigorous thinking.