I have presented yesterday a hot glue stamp.
If you press it into foam now you get a foam stamp with hot glue imprint ;-)
Links:
Foam Stamp with Hot Glue Imprint (How to: Artist Trading Cards DIY, Swap & Contest) (video)
via: How-To: Make Rubber Texture Stamps for Artist Trading Cards
Here at unikatissima:
Hot Glue Stamp