Use any of the following sites to practice subtraction skills:
mrnussbaum.com/uploads/activities/dragnew/index.html
http://www.oswego.org/ocsd-web/games/Mathmagician/mathssub.html
http://www.amblesideprimary.com/ambleweb/mentalmaths/subtractiontest.html
http://www.oswego.org/ocsd-web/games/SpeedGrid/Subtraction/urikasub1res.html
http://www.oswego.org/ocsd-web/games/SumSense/sumsub.html
http://www.kidsnumbers.com/subtraction-action.php
http://www.kidsnumbers.com/subtraction-mathatobie.php
http://hoodamath.com/games/numbereaters.php
http://www.fun4thebrain.com/subtraction.html
http://www.quia.com/rr/10279.html
http://www.dositey.com/addsub/mystery2SS.htm
http://www.sheppardsoftware.com/mathgames/Numberballs_subtraction/numberballsSubtraction.htm
Two Digit Subtraction:
http://www.coolmath4kids.com/subtraction/05-subtraction-lesson-two-digit-numbers-01.html
http://www.coolmath4kids.com/subtraction/06-subtraction-lesson-two-digit-numbers-01.html
http://www.learn4good.com/games/kids/double_digits.htm
Three Digit Subtraction:
http://www.coolmath4kids.com/subtraction/07-subtraction-lesson-three-digit-numbers-01.html
Subtracting Across Zero:
http://www.harcourtschool.com/activity/elab2004/gr4/3.html