We are lucky enough to have actual fraction tiles for use at school as well as online access to our current textbook at PearsonSuccessNet, but I thought that this virtual manipulative would be great for kids to use at home.
Here is a screen shot of one of Houghton Mifflin's many virtual manipulatives. Our school is transitioning to their Math in Focus / Singapore Math program grade by grade, so I have been trying to get ahead of the curve and check it out before it gets to my grade. I really like this one because it's easy for me to model on the Promethean Board and easy for the kids to use at home.
If you can't access any of the above for use in your classroom or for your students at home, try printing these fraction strips by clicking on the pictures.
Illuminations (from the National Council of Teachers of Math) also has free virtual manipulatives, lesson plans and worksheets for understanding, comparing, and ordering fractions.
This one is really neat because it also shows decimals, mixed numbers, and percents!
(this one is more challenging than my students can handle - might be good for G&T or older students)