Conceptua Math Fraction Tools are great Interactives for helping your students understand Fractions. The site has tools to help understand fractions on a number line, add & subtract fractions, identifying fractions, estimating, equivalents, finding common denominators & more. Not only do they have interactive tools for visualizing each concept, they also have a video for how to use each tool, common core aligned standards for the tool, lesson plans and classroom activities (with a premium membership).
The site and fraction tools are free to use, but you do have to sign up for a free account to use the tools. You can sign up for a premium account if you would like detailed lesson plans as well as student individual logins.