Georgia Performance Standards
This link will take you directly to the math framework for 6th grade. All sixth grade students must learn the same standards and use the same textbook. I follow this very closely and use some of the projects listed on the website. Though they say they expect this out of all 6th grade students in the state of Georgia, I think you will agree it is quite challenging!
https://www.georgiastandards.org/Frameworks/Pages/BrowseFrameworks/Math6-8.aspx
Illuminations!
Illuminations is a wonderful website from the National Council of Teachers of Mathematics. It include exciting lessons and practice for every grade level.http://illuminations.nctm.org/
From the illuminations site is a lesson the students really enjoyed regarding symmetry and transformations.
http://illuminations.nctm.org/LessonDetail.aspx?ID=U134
Holt Web Help!
Your student's textbook comes equited with a web-site to help the student and the parent!
http://go.hrw.com/gopages/ma/msm1_07.html
Interactive 3D Shapes
This is a great link for studying 3-Dimensional figures and their properties.
www.learner.org/interactives/geometry/index.html
Create-A-Graph
This is an easy to use site for students just learning how to make computer-generized graphs.
http://nces.ed.gov/nceskids/createAgraph/default.aspx