Use rolling pin to make an imprint on clay. Pick a flower or plant and lay on top of a small piece of clay and use a rolling pin to make an imprint in the clay. let it harden. -These would make pretty magnets.
DIY :: Acrylic paint (enamel works even better, but it's more expensive) on a few smooth rocks, then placed here and there in the garden, makes a surprise treat for the eyes. Summer project for the kids. Hobby Lobby has rock painting kits.
CoOl DIY - Book Paper Flowers : Make paper roses decorations to add an interesting twist to items including gifts and Christmas tree ornaments. To find out how to make your own paper rose, read this tutorial.
Silk flowers dipped in plaster-of-paris: You may have seen some plaster dipped items previously around the web. But I quite like this idea and thought they warranted a little time in the spotlight. Specifically, dipped faux flowers.