Here's a very inexpensive way to work on the concept of one-to-one correspondence! I adore the dollar section at Target! I found these super cute tin pails and a bag of pumpkin erasers. I already had an unfinished wooden cube that I used a Sharpie to make into a pumpkin dice.
The activity can be as open-ended as you'd like. Twiggy and I would take turns rolling the dice and putting the corresponding number of pumpkins into our pail. We played until the pumpkins were all gone, and then counted our stash. We talked about who had more and who had less.
* Use the dice to "take away" pumpkins.
* Use ice-cube trays as grids. Whoever fills up their tray first wins.
* Get a second type of eraser (we also bought bats) and practice patterning.