One reason I've been collecting activities is to find things to do for my little guy, who watches too many movies. Right now he is really into puzzles. He did a math puzzle yesterday, and he really likes a construction worker puzzle. He has also been doing dinosaur puzzles.
He plays "the number game" as often as he can find a partner.
Another recent favorite is Hi Ho! Cherry-O, which teaches math, especially if you include addition and subtraction language (adding 2 cherries to the bucket).
We played Triominoes yesterday, and the kids lined up some regular dominoes to knock down.
We also played chess yesterday. I have kind of talked up the game, and both kids like to play. P. tries to get on my computer to play. It only lets him make legal moves, so it's easy.
J and I sorted buttons to make a color work for a friend. I just noticed that the rainbow colors do not go clockwise, which would be my preference (L-R, T-B).
One thing my kids like to do is sing our family's version of "We are the Champions" when they win a game. It's a small thing, but it's fun for the kids. Playing games has been good for discussions related to winning, the enjoyment of playing, cheating, and setbacks being "part of the game."