Make some origami boats to float in the puddles.
Raincoats + Chalk= Lots of fun! Picture from Our Unexpected Journey.
They realized chalk works better in the rain!
Squidoo.com suggested putting food coloring in a big puddle and add a few squirts of dish soap then blow with a long tube and you should see a bubble explosion!
And if all else fails there is always puddle jumping! Check out the rest of her cute outfit here.