You can use the cross-reference feature for Categories.
- go to Products > Manage Products > New/Edit Products;
- open a Category, where you have the Product and open the Product (just do a double click on the Product or highlight it and click "Quick Edit");
- go to the "Categories" tab under the Product settings;
- choose a Category(Categories), in which you want to see the Product and clicl "Add";
- Save the Product.
Here are some screenshots: