We've used all kinds of manupulatives for pre-k/k/1st grade, I really enjoy finding new manipulatives to illustrate a concept. I would say we use the blocks that come with our math u see program are used the most and they are great.
Here are some others:
-tangrams, just simple cardboard ones plus a book called 'grandfather tang's story' which uses the tangrams to make animal shapes
-unifix cubes, a couple hundred of them but they end up getting more use as building blocks than as a math tool
-unifix stair, really great for pre-k level to show how numbers are not just a squiggle on a page but represent a sum and those sums increase as you count higher
-unifix patterns, it's a plastic graph looking thing with interchangeable papers so the kids can put the unifix cubes over the colors on the paper to make patterns or use the blank sheets and crayons to design their own patters, more of an educational toy than a math manipulative (imo)
-pattern blocks and cards, again it's a toy kind of thing but I feel is very educational. There are thick (about 1cm) pattern blocks which are sort of like tangrams and cards to help build animals and other shapes with them. They have many more possibilities than just the cards.
-three dimensional shapes, these are just a bunch of little plastic three dimensional shapes I picked up for a few dollars at a conference. Before I had tried to build my own and they didn't turn out very well (but did show how, for example, a pyramid is a square and four triangles well). They kids like getting them out to look at and quiz one another on what the shapes are.
-teaching clocks, we have two cheapy/flimsy ones that no one like to use and one small judy clock that everyone want to use. It's helped a lot with learning time and I plan on getting one of each of the kids.
-play money, we started with real money but once they grasped the coins it got to be a lot of cash to have out so we switched to an inexpensive set of play money and plastic coins. The entire set was only a few dollars and it's serving it's purpose well.
-counting bears, these really are for early kindergarten and before. we have the pattern cards that go with them as well but they don't seem to get much use from the kids once they reach kindergarten level work. I do plan to get a balance scale and since they are all numbered with their weight it should be a good lesson in equal sums.
-peg boards, these are just being used like a toy for now. I try to have the kids make geometrical shapes with them but they often go off and make their own shapes with the rubber bands.
-number line and number board, the line for the wall and the smaller laminated 1-100 wipe off boards have been very helpful in learning numbers to 100 and serve as an easy reference while doing math
-unifix number cubes, just like the regular cubes but with numbers on them and with things like addition signs, equal signs, and all the way up to square root signs, parenthesis, and so on; seems to be more fun for me to build algebra equations than for the kids to practice subtraction facts
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