I went to Home Depot to buy the plywood and took a crate in with me. They were able to cut it to the exact size I needed. The guy that cut it messed up on a few and had to re-do them, so they didn't charge me extra for the extra cuts. Even if they had, it would have only been 50 cents per cut after the first three, I think it was.
I found the fabric on sale at JoAnn Fabric. I bought 3 yards of one fabric (for the blue and red crates) and 2 yards of another fabric (for the pink crates). I used a 50% off coupon at A.C. Moore to get the stuffing. Later I found out that fabric "quarters" are the perfect size. It actually would have been a little cheaper because WalMart also had them for $1.
A few fabric cuts and nails from a nail gun later, I was finished!
Here's the first one I finished (I was so excited I had to take a picture to send to friends and post on Facebook right away!)
This is the same fabric I used for the red crates. The fabric I used for the pink crates is the same pattern but white with orange and different shades of pink for the dots.
I used the crates for seating at one of my small group tables in my 2nd grade classroom. Since then I've gotten rid of my desks so that table had to become a regular seating table with their chairs with backs. I'm still looking for a replacement table so my crate seats can be used once again! Until then, they're still used for storage and are available if a student would like to sit somewhere to read other than their table.