The National Library of Virtual Manipulatives is a wonderful resource for teachers and for students that need manipulatives for math computation. Many students can benefit from using them, but there is not always a ready supply for use. Note, your Java has to be up-to-date for this site!
You can search by grade levels or topics. There are manipulatives for fractions, base ten, geoboards, clocks, transformations, money, charts, graphs, number lines and more! This site supports K-12.
Fifth grade teacher in a 1:1 iPad classroom, sharing my journey with technology in the classroom