This is one of the coolest sites I have seen in awhile. We all use base ten blocks for some reason or another. Either place value, adding, subtracting, and many other reasons. At this site you can use base ten blocks to do all of this. You've got one, tens, hundreds, and thousands. My favorite part is it will regroup for you. If you have a tens rod, you can drag it into the ones block and it will split apart into 10 ones. This site is awesome!
Using technology with computers in the classroom.