We have a little math aficionado at our house who makes up addition problems for fun when she's bored. So she jumps right at those opportunities to do math worksheets. We are cruising through Math U See Primer right now, amongst other mathy stuff.
Whether you have a math lover or want to slip math in unobtrusively, there are some great picture books that teach math concepts. And our Top 10 feature writer over at Winning Readings, Michelle of Little Nippers, has a great Top 10 list of math books for you this month - mostly for the age 4-8 range. These are going on my library wish list for sure!