Mathwire blog - lots of ideas that could be used for workboxes. This link takes you to their index by grade. A lot is worksheets but there are games in amongest the worksheets you just have to look for them. Sue does talk about adapting worksheets in her book to make them more interesting and this site does have some fun looking worksheets.
Worksheet Generator for extra practise
Math worksheet creator site – make your own worksheets this is one of the easiest to use I have seen. You can also print out an answer sheet at the same time. http://www.superkids.com/aweb/tools/math/