Asking students to explore new concepts with these virtual manipulatives can be great when combined with a lecture or reading activity. Afterwards, it can be powerful to bring the class together, look at the virtual manipulative again, and have them reflect on what they've learned. Also, these manipulatives could be assigned as homework, or as a supplement to traditional practice problems. Parents may find it helpful to be able to "play" with these tools alongside their child. While the site doesn’t give many specifics to teachers, there are lots of potential uses here. Teaching algebraic thinking to elementary school students? Just display one of the interactive games or demonstrations on the board, or let students explore it on a laptop with just some simple instructions. Even in small groups, these tools are engaging and effective.

Continue reading**Editor's Note: While the National Library of Virtual Manipulatives is still available but the manipulatives require outdated Java software that's incompatible with most web browsers.**

Dating back to 1999, the National Library of Virtual Manipulatives (NVLM) is a collection of Java-based interactive tools that teach math concepts. While some of the concepts can be quite complex, most of the tools have a very simple (and dated) appearance. However, they'll run on any Java-capable browser (not on Apple's mobile devices). On the site's home page, users find a Virtual Library containing tools under the following categories: Numbers and Operations, Algebra, Geometry, Measurement, Data Analysis and Probability. Each category is divided into resources for different grade levels, from Pre-K through 12^{th} grade.

The idea alone of a library of manipulatives like this is a novel concept; after almost 15 years in the making, the site still has a lot of potential. However, an update –- not only to design but usability –- would be a great way to make this site accessible to more kids. That said, given the tools' exploratory nature, the site can be great for allowing students to discover math concepts on their own. By experimenting, students are often more successful in building deeper understanding, and even though the site gives little in the way of direction, it can be great when used in this way.

If using these tools to support specific parts of your curriculum, you'd be wise to help students along; either direct them toward areas of focus, or give them some context by showing them examples beforehand. Because not all the manipulatives give kid-friendly feedback, the site would do well to build in some better interactivity. Also, for your visual learners, the NVLM can be great for helping kids see and understand abstract concepts like variables and statistical probability.