Here is a website that offers virutal manipulatives from Glencoe/McGraw Hill. You can select grade levels, background templates, and different manipulatives.
Another website is from the National Library of Virtual Manipulatives. From this site, you can choose different math subjects for different age levels. For example, you can choose Number and Operations for grades K-2, or Algebra for grades 3-5. There are excellent manipulatives in each category.
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