http://go.hrw.com/gopages/ma.html - online book
http://www.khanacademy.org/ - KHAN Academy - extra practice problems and lesson videos.
http://familyinternet.about.com/od/websitesforkids/a/Math-Websites-for-Middle-School.htm - extra practice and problems of the day
http://www.aaamath.com/fra.html - this website is devoted to understanding fractions (addition, subtraction, multiplication, division, etc.)
http://alline.org/euro/mmath.html - download free measurement convertor to help with metric conversions and customary conversions.