K-5 Math Teaching Resources; has LOTS of freebies, but i purchased the Math Journal pack for $7 and was well worth it. Problem solving questions for all domains; encourages writing, collaboration, those "AH HA" moments we teachers love when they work through problems.

http://www.k-5mathteachingresources....-journals.html
I recently got their Common Core Vocabulary since we are starting that next year. However, this year, I use what they have on their site and it is extensive. Lots of math games for centers for subtraction too!