i Ready - https://login.i-ready.com/
Imagine Learning - http://imagine.caldwellschools.com/ile?studentlogin
Great Sites for Math and Reading Practice:
www.firstinmath.com
http://www.mrs.henderson.k12.nc.us/EOG
http://www.abcya.com/third_grade_computers.htm
http://www.studystack.com/Math