Greatest Common Factor Problems with instant feedback for your answers
http://www.aaamath.com/g72b-grt-com-fac.html
Working Factor Trees Online
http://nlvm.usu.edu/en/NAV/frames_asid_202_g_3_t_1.html
practice identifying decimal place value
http://www.321know.com/plc51cx2.htm
identify prime or composite numbers with instant answers
http://www.aaamath.com/g57-prime-or-composite.html
Number cop - type a name then scroll through the "other games" menu and select prime numbers. try to hit the prime numbers with your car by by moving the arrow keys.
http://hotmath.com/hotmath_help/games/numbercop/numbercop_hotmath.swf
identify prime numbers with instant results - type in the maximum number as 100 and then get started.
http://www.softschools.com/primemain.jsp