http://www.lil-fingers.com/games/time/index.html (telling time to 5 minute intervals-students manipulate the hour and minute hands)
http://www.mathplayground.com/quick_math.html (students have to insert the correct operation sign for number sentences-timed)
http://www.ixl.com/ (skills for all grade levels)
http://www.funbrain.com/tens/index.html (place value and rounding)
http://pbskids.org/cyberchase/games/ballparkestimation/ballparkestimation.html?2 (estimation for 3rd/4th grades)
http://www.funbrain.com/cgi-bin/ofm.cgi?A1=s&A3=0&A2=0 (ordering numbers-2nd grade)
http://www.crsd.org/50338927131259/blank/browse.asp?A=383&BMDRN=2000&BCOB=0&C=53383 (tons of different math games)
http://www.mathplayground.com/GrandSlamMath1.html (2nd/3rd grade one-step word problems)
http://www.mathplayground.com/GrandSlamMath2.html (3rd/4th grade one-step word problems)