There are many websites that provide educational resources targeted to elementary school math curriculum, including Education.com, Mathplayground.com and Kids.usa.gov. Which sites are appropriate depend on the age of the child and the local curriculum.
Education.com allows users to filter available worksheets and activities by grade level and the specific math skill, such as probability. The resulting activities can be downloaded, printed and facilitated by a classroom teacher, parent or other appropriate adult.
In contrast, Mathplayground.com is aimed at the students themselves. It contains many games that teach and reinforce math skills, from addition and subtraction to pre-algebra. Because the activities are formatted like computer games rather than worksheets, children are more likely to actively seek out the activities in their free time. The games are free, and can be played in the web browser of any computer.
The math resources available on Kids.usa.gov are targeted to teachers and parents to use alongside the children. There are some simple math games that children can play by themselves, along with pre-written lesson plans and activities using inflation records and census activities to show the practical applications of mathematics. The site also features a self-assessment tool that students and their parents can use to measure their progress.