This membership-based website offers practice problems. Answers and explanations are included. It is a fee-based website but it looks worth it. Thank you to the Kraak family for showing me this website. www.IXL.com
Links for students, parents and teachers. Links are arranged by topic and include lessons, games, timed practice, remediation, contests and enrichment. http://www.bobsedulinks.com/math.htm
Do Math: NCTM page featuring activities kids can do on their own or with families. Includes a link to Nasa space simulator and to the government hurricane center. http://www.domath.org
Figure this: NCTM page of math challenges for families to ponder and solve. http://www.figurethis.org