Wow, can't believe September has passed by so quickly. Ds4 (my 3yo) and I studied about the farm this month. It was a blast! We read lots of books, did tons of coloring and even play-acted being farmers in the backyard with pretend and real tools. And we compiled a lot of our endeavors into a lapbook. :)
Also a cute little book called Duffy On The Farm. Some of the resources I used for this study were The Mailbox Thematic Unit for farms and the farm and zoo lesson plans from Kinderplans.com.
Here's the cover of ds's lapbook and what it looks like upon opening. You open the barn door and see what large animals live on the farm, and you slide the strip across the hayloft and see what smaller animals live there. The barn outline and the pics of the animals are from Kinderplans, but I made up the little sliding thing. There are little booklets about what baby animals live on the farm and what sounds farm animals make, as well as a math activity where he had to add the correct amount of spots to numbered cows.
The top pic here is of some worksheets from The Mailbox book, re-telling the Little Red Hen story and another one teaching prepositions that you can't see. The bottom pic is off some little arts/crafts things we did. I tried to find a farm in our area that would host a tour for us, but in our neck of the woods it's more about peanuts and cotton fields. This was a fun unit with plenty of resources available from your library and the internet. :)