Playground Build & Design | Natural Child Play | Earth Wrights Ltd
I like these examples of gross motor components that are embedded in the landscape and offer a variety of interactions, yet (maybe) aren't high enough from the ground to require safety rails, etc.
This blog has many ideas for outdoor instruments, including this suggestion that uses PVC piping.
Creative Play - Natures Instruments
Adventures of Adam DIY Toddler Water Wall. Easy to make water wall using recycled plastic bottles. Great for toddler outside play.
Homemade Scales at Baxter Pre School Inc. - image shared by Natural Play for Children - so cool!
Our children are very busy at the music wall! It's a great DIY creation from pallets
An inviting and inexpensive way to add music outside. I would tweak it a bit for safety and easy access for preschoolers.