After posting all of those wonderful DIY stamp ideas, I had to try a few of my own. These stamps are really a combination of a few of the others, but are closest to this herringbone stamp from A Beautiful Mess.
I was a little worried that using craft foam sheets wouldn't work very well, but it really did. It was so easy, and I know I'm going to make more.
What you need:
1. Craft foam sheets
2. Glue + Scissors
3. Small wooden block
What you do:
1. Cut out the shapes that you want. (Remember the stamp will be a mirror image)
2. Cover the wooden block with a layer of glue.
3. Place the foam pieces on the block. Press down to make sure that they all dry flat.
I also made a stamp for my blog logo, and for my (upcoming) etsy shop. The foam works best with simple geometric shapes. I found that it lost a little bit of detail on the more intricate shapes. However, it still worked well and was very easy.