Here's a little look at different materials and techniques that I found by briefly looking on Pinterest. Then I surfed a bit on the internet. Some are very simple and would be easy to do with kids. Others might be better suited for adults.
Stamping with pool noodles
This is a great way to stamp on paper with kids, using a pool noodle.
Stamping with pencil erasers
Usually when I stamp on paper, I'll buy or carve my own stamps. But here's a real simple technique that Carloe used with a pencil eraser. Didn't it come out pretty!?
Stamping with vegetables
I remember in grade school, we used potatoes to stamp on paper. Do you remember that? Here's a post from Crafting with Kids.
But have you every used an okra?
Stamping with Nail Polish
I've seen some ladies walking around with crazy-designed nails, and thought the whole nail was placed on top. But Helen has actually stamped right onto her nails. She can show you how to do it with just a few products, in a quick video!
Stamping with buttons and Martha Stewart
Martha Stewart has a great idea on her website: stamping using buttons. I know there are some of you out there that would love this!
Stamping with Gelatos
Let me end with this cool site by Donna Downey, who has lots of scrapbook and journaling tips. Here she used gelatos for stamping. I've never heard of gelatos before; well, except for the Italian ice cream. These are creamy watercolor sticks, like chapstick, from FaberCastell. I found some at JoAnn's.