When my kids were young, I loved the free, laid back days of summer and I remember how hard it was to get them to do school work then. It is very important to keep the skills fresh in your child's mind, so that when they return and enter first grade, they will not have to play "catch-up". I recommend that you work on the kindergarten skills for review. Maybe you could have a set "school time" where everyday or certain days at a specified time you work on some skills. Keep it light and fun. Maybe he/she could have a sticker chart where they could earn a sticker for each session and earn prizes like: a picnic day, a birding hike, a beach ball, playtime at the park, etc.
Remember to limit "screen time" with your child. Kids love TV, video games and computer time, but we all know that it is not good for them to spend hours at a time sitting in front of a screen. Be strict about that now before they get older as it becomes more difficult then. Set a timer and when time is up that is it. Your child will be all the better for it. Then they need to get outdoors, read or do something else.
They can do reading and math nearly everywhere and anytime. At the store you could have him/her read your grocery list or read words in the store. They could read signs while in the car. They can do addition and subtraction while setting the table or eating their food. Be creative! Help your child see how what he/she is learning in school is relevant to daily life.
There will be a list of summer workbooks coming home that you may purchase. There also are many awesome websites for you child to utilize. My wiki space also has many ideas:
http://armourkindergarten.wikispaces.com/
Here are some ideas for learning time:
Language
Read the reading booklets that I sent home each week
Study the Word Wall and have him/her learn how to spell and write the words too.
Have your child write the grocery or "to-do" list.
Practice writing sentences or write a letter to a loved one or ME either by mail or email.
Go to the city library! It is a cool place and they usually have a fun summer reading program with prizes! We are so fortunate to have that library, so we might as well take advantage of it.
Math
Work on addition and subtraction flashcards with sums up to 10.
Give your child story problems to solve.
Review the coins.
Name and write numbers 1 - 30.
Count to 100 by 1s, 5s, and 10s.
Name and find shapes in their environment.
Make and extend patterns.