Addition and Subtraction Fact Practice

Mathsadd - Super activity, easy to use (type answer then hit Enter), large
                    numbers, facts can be  selected. 

Ambleweb Addition Machine  - different levels allow you to do double digit addition

Sumsense (addition) - A clever activity in which you make the add fact (click and drag) 
                                     from a set of  numbers.

Sumsense (subtraction) - Same as above only for subtraction facts.

Speedgrid 1 (Addition) - Find two numbers on the grid that add up to the given
                                         number; a really neat activity. Level 2  Level 3

Speedgrid 1  (Subtraction) - Same as above only for subtraction. Level 2   Level 3