This is a great site for activities that test students in a fun interactive way. Includes a lot of math but also some science, languages, and geography.
Fun math game with several levels of difficulty.
A site of math games and activities where you can create an avatar and stroll around to your choice of different math topics. The graphics are really well done and it allows for users to log in as parents, teachers, or students. Age categories run 6th grade and lower, 7th grade, or 8th grade and higher.
Math work for all levels. PDFs and online activities.
How to use a classroom twitter account for math and/or writing prompts