If you are using puddles you could add poster paints, bubbles, smells (aromatherapy), leaves, twigs (floating and sinking experiments)...
Then we go through them with bike wheels, cars, wellies etc to see the patterns...
then collect some of the rainwater to take inside to look at carefully using the microscope or magnifiers to spot what else might live in a puddle.
Songs might include 'listen to the rhythm of the falling rain' by the Cascades -
http://www.youtube.com/watch?v=bQstQST1GiM;
enjoy
