We love pattern blocks. It's like a big bucket full of tangram pieces, basically. All different shapes and colors, and they're great manipulatives for working on fractions, arithmetic up to and including division, geometry, symmetry, squares & cubes, triangular numbers, area & perimeter... Plus they make darn good Transformers if you're feeling artsy. (Okay, they make flowers and houses and patterns, too. Yes, okay...) But seriously, my DS7 and DS4 can play with them virtually all day without a break. They love them!
Tangrams are also great fun, but are slightly less open-ended.
A big old pile of symmetrical wooden blocks can be good for working on squares, cubes and triangular numbers, as well as number patterns and forecasting based on patterns. (If a cube with a side of 2 has 8 blocks in it, and a cube with a side of 3 has 27 blocks in it, how many total blocks would a cube with a side of 30 blocks contain?)
Doing work with different number systems is fun and can be done with or without manipulatives. Base 2 and base 12 are fun ones. You might also look at stuff like Roman numerals or other ancient and less commonly known systems like the ancient Sumerian system.
Baking is a great math journey. All the fractions! How many cups in a quart? How much does a cup of flour weigh? How many liters in a gallon? So many things to look at there!
Dice! You can make up any number of games if you have a handful of dice! We rolled 6 dice and DS7 had to come up with equations. Pretty much any combination he could come up with was allowed, so a 1 and a 6 could be used as 7 (1+6), 1/6, 6/1, 5 (6-1), -5 (1-6), etc. That allowed a lot of combinations. If you can get 10-, 12-, or 20-sided dice, even better!
I'll keep thinking--we've got lots!
P.S. I strongly recommend shopping the sale sections of online educational stores like Didax.com. You can get some real steals on stuff, and I'm personally much more willing to take a risk and try something new if it costs me less than $3! If it's a bust, well, it was a gamble, but not a big loss.
