
Visual Fractions has eight categories of visualizations, lessons, and games for students to explore and learn the functions of fractions.
Fraction Bars developed by Albert Bennett has interactive activities and visuals for students to use to develop an understanding of fractions. One of the activities that I tried out had students drag fraction bars into an equation to test solutions.
The National Library of Virtual Manipulatives has a lot of interactive activities for students learning the use of fractions, addition and subtraction, and the multiplication of fractions.