Counting is one of the easiest activities to do at home. Counting during dinner, snack, or even house hold chores will help further your child's proficentcy with their math skills.
When driving in the car point out signs of common stores and resturants. By acknowledging the signs have a name you are helpping your child become a reader. Environmental print is one of the earliest forms of reading and a great stepping stone.
Go on letter and number hunts. Young children love to play games and this is an easy and engaging way to increase letter and number recognition. One way to do this is to buy a pack of index cards and write capital letters on one side of the card and the corresponding lower case letter on the other side. Do the same with numbers 0-20. (With your number cards you could also write the number on the front side and then place the same number of stickers or colored dots to the other side.)