Make musical instruments from "clean" garbage. Have some garbage items and craft items (cans, bottles, jugs, rice, cereal, string, rubberbands, glue, cardboard, jars, sticks, etc...). This is a good way to recycle old garbage items in a creative way! (this is also a project I intend to have my students do once I have a regular music teaching job)
Nature rubs: have the kids take a few pieces of paper and some crayons and make rubs of things such as tree bark, rocks, or anything cool they can find to make a texture on their paper. (then for the art portion have them make picture frames for their pictures!)
Just something fun to do: It's called "Rain"
Have the kids in a line-ish formation. Start at one end having the kids follow what you do. When you get to the end of the line, go back and change the action. It will sound like a tunderstorm coming and going because of the overlapping of sounds. Here's the order:
Rub hands together (swishing sound)
Snap fingers
Pat lap
Clap hands
Stomp feet
Clap hands
Pat lap
Snap fingers
Rub hands together
Stop
Hope some of this helps!