There are so many wonderful resources online now for math enrichment! I love looking at all the suggestions on Pinterest, etc. As with any type of programming, different approaches may work better for one child than another.
I used Singapore Math with both my boys (not the new, dumbed down versions available to kids in public school that complies with Federal mandates for ridiculousness via Common Core). I continue to feel that it provides a very solid base for math studies, although some children may need more practice work in order to cement facts. There is an American version out now, but you actually get more work with non-standard units of measure if you use the original version.
You can look inside the book here: http://www.rainbowresource.com/product/sku/023977
This is the U.S. edition. If you'd like the original, then search at the above site for "Singapore Standards Edition."
There is a textbook and a workbook for each semester (so four books for first grade). There are also home instructor guides if you feel you need help with how to present the programming, ideas for extra work, games, etc. There is an answer key for books 1-3 all bound together. Additionally, you can get extra practice workbooks, "intensive" practice workbooks (more difficult problems), math challenge workbooks for some levels, etc.
These books are quite reasonably priced, even new!
For the beginning grades, I feel that while they do a good job of covering basic math, children do need extra work with what I've always considered "morning math." This includes things such as place value, calendar math, money, time, basic geometry, etc. I always cut my classes up into small chunks of 10-20 minutes (depending on the child and his needs). I would cover different math topics in three sessions during the day so that it did not overwhelm them. In one session we would do our Singapore math for the day, in another we would generally cover time and money until they became quite proficient at it, and in another we would cover various of the other topics each day.
I always liked the Complete book series for colorful worksheets at this age. One big book can easily be used from K or first through about third grade.
Here is a link where you can look inside (there are several different cover styles with the same content inside);
So, we used the more simple work, generally organized at the beginning of each section, for first grade, then saved the medium level work for second grade and the more difficult problems for third grade. Half the book covers time topics and the other half money topics.
We also interspersed various card games, board games, and other activities into our daily practice in order to break things up. Sometimes these books include suggestions for games, too.
This series even includes a Complete Book of Math Games, although I have never looked at it. It probably pulls game ideas from its other math books:
Here is a website that offers more ideas regarding time and money math, including a free unit on each that can be downloaded:
A fun book by the Maestros (and see the one on clocks and calendars, below, too):
For calendar math, we always used a wipe off calendar that included fun clings. Here is one I found online that is available now:
I feel sure other companies still offer these, as well. At the beginning of each month, we set up the new calendar, then we use it throughout for various projects. This set also includes seasons and weather, so you could incorporate science activities into its use, as well.
A fun book by the Maestros:
Here are some websites with ideas for working on other areas of math:
This site uses a lot of 100 chart activities. One other thing we did was start a "number scroll." There are printable grid sheets for this that can be taped to a paper towel roll and then as you finish each sheet (about a hundred numbers go on a sheet), you glue it to the end of the last one and roll it onto the tube. As the year goes on (and we continued this into third grade), your scroll grows and the kids find it fun to unroll and look at. It works on number sense and place value. A lot of times kids have trouble transitioning from one set into another, such as from 399 into 400, 401, 402, etc.
We also did LOTS of skip counting!
Here are a few more ideas for skip counting:
Here are some different options for forms that can be used for some morning math work (limited areas of practice):
Lots of good ideas here for various morning math topics, including lots of songs:
Downloadable calendar math notebook:
(Hopefully will be updated for next year, or at least some elements of it can still be utilized....)
For geometry, have geoboards, tangrams and geometric solids on hand!
This wonderful math site also has all sorts of other areas of math covered for you - just click on first grade!
Symmetry and Venn Diagrams can be used for science, too!
The site has online tutorials, as well:
(This is just one example page....)
You can incorporate sorting or patterning work through geometric shapes, too:
We used our Tangrams for that a lot....
We had a Melissa and Doug set of Tangram puzzles, among others:
As you can see from a puzzle like that of the sun, you could use it for patterning and symmetry work, as well.
We incorporated living books, too, for math studies as well as language arts studies! A fun book never hurts to break up the monotony of worksheets.
I'm sure I'm forgetting some of the areas of math we covered at those early grade levels - there's SO MUCH! However this is all I can think of right now. More, later, on other topics of study, such as history and science....