One thing that we use almost every week is a set of number flash cards I made up about a year ago. I took 50 3x5 cards and on half of them I wrote the numbers 1-25 and on the other half I put the corresponding number of stickers. I laminated these for durability.
When it's number day for preschool I often will take these out. There are so many things that can be done with these versatile cards. Trevor practices counting the number of stickers on the cards and also tries to match the numeral card with the card that has the correct number of stickers. You could have youngsters practice putting the numbers in the correct order or even have them simply identify the number.
Something that I work with Trevor on, but is still too difficult for him to really get, is matching the number card with its sticker card without actually counting the stickers. This week I got out three sets of cards, the 5, 9 and 12 sets, and asked him different questions to hopefully help him start to get this concept. I asked him things like...Which card has the most stickers on it? What number is the biggest? What card only has a few stickers on it? Looking at items relative to one another is a pretty abstract concept for him still, but it's good to help him understand differences like big/small, many/few, etc.