Number Sense

Number sense in kindergarten and first grade is the ability to understand the relationship between numbers and quantities (i.e., that a set of objects has the same number of objects in different situations regardless of its position or arrangement). It also is the ability to understand and describe simple additions and subtractions and to use estimation strategies in computation and problem solving that involve numbers that use the ones and tens places. 

Here are 2 websites with activities to help build number sense.

http://www.aaaknow.com/kinder.htm

http://www.aaaknow.com/grade1.htm