I had so much fun making these costumes for the grandboys. The overalls tutorial is here and the hat tutorial is here. They were very easy to sew using fleece fabric which has a good stretch and doesn't require any seam finishing. I got the giant yellow buttons from eBay and the gloves (89 cents/pair!) from Wal-Mart. The most difficult things to find were the shirts, believe it or not, especially the green one. It seems that almost all kids' tees these days have graphics and it's hard to find plain solid colours. I eventually ordered them from Lands End.
Here they are on their way to a block party.
(sorry for the blurry iPhone photo)