PBS Parents: Helping With Homework, http://www.pbs.org/parents/education/going-to-school/supporting-your-learner/homework-help/

Sponsored by PBS, this site offers practical advice for parents on many educational topics of concern.

Teachers Involve Parents in Schoolwork (TIPS) Interactive Homework, 
http://www.csos.jhu.edu/P2000/tips/index.htm

This site offers guidelines for interactive homework, with examples for language arts, math, science, and social studies, as well as blank templates to use for creating activity sheets.

The University of Chicago: Everyday Mathematics, http://everydaymath.uchicago.edu/parents/

This Resource Center site hosted by the University of Chicago offers support to parents with grade-level math concepts. The links include games, tutorials, simulations, and teaching tips.

U.S. Department of Education: Helping Your Child With Homework, 
http://www2.ed.gov/parents/academic/help/homework/index.html

This extremely helpful PDF offers guidelines and additional resources to support parents in their quests to help their children with homework.