Draw a Number is a great independent activity for students to use as a filler/sponge or in an independent center. It provides continual practice with rounding, place value to the hundred thousands, and addition/subtraction to the hundred thousands.
All you need is a deck of cards. Remove the face cards and 10's and you are ready to go!
You can find other great activities on my website at www.TreasuresForTeachers.com