I made four cards, wrote the numbers at the bottom of each card (always slipping in literacy whenever I can!) and marked each card with dot/s to represent the numbers.
Then we sat down with a pile of wooden blocks and went through the cards. I asked her to count the dots on each card, and asked her to put a block on each dot. She did that quicker than I had anticipated, so I extended the game to become a kind of maths-skills-primer. I took cards 1 and 2, and asked her how many blocks were on each, then said "1 + 2 = how many blocks?" and put the two cards side by side. She counted them and said "three, Mummy!" She just did her first sum!
So, when I get a chance I'll be making cards up to 10 and repeating the activity to see how much she can confidently handle. Even if your toddler is still quite young, you can adapt this activity to help them learn their numbers. If your tot is older, you can increase the difficulty to help them learn basic maths skills.
A word of caution though: try not to push your child to do these sorts of activities - the aim is to appeal to their interests and offer them opportunities to learn, not to force it on them, especially at such a young age. Keep it short and sweet (in keeping with their attention span) and don't offer it when they're clearly not in the mood, it will just frustrate you both. If you're sensitive to your tots feelings/wants when you introduce this game, you may just be surprised at how much they know (I sure was!).