One of the most helpful books has been Teaching Physics With Toys: Hands-on Investigations for Grades 3-9 for which I discovered the KNEX educational sets and instructional materials to introduce fun simple machines to my students. I've included a few pictures of what they've experienced.
Pulleys with KNEX flag pole and sailboat - and a classroom clothesline hung with real pulleys to experiment.
Gears with a KNEX windmill with 3 sizes of gears- and a game called Top Gear I found on EBay, as well as an old-fashioned hand egg beater, which several students used to beat whipping cream to butter!
We also experienced levers, real and modeled see-saws, wheelbarrows and shovels and spoons. (KNEX wasn't really needed here.)
And most of them have at least some understanding now for the physics concept Work,which lies behind all simple machines. The unit ended in the construction of small models of the three simple machines, which now decorate the classroom wall instead of inspirational posters.
Now we've taken on electricity and magnetism, constructing small motors and inducing both magnetism and electricity. Tomorrow is the fun static electricity day with balloons and a list of materials to figure out which gives and which receives electrons - encroaching a little on chemistry while we're at it. And then they get to dig into what's behind the old game "Operation" to see what a circuit consists of - using a lesson plan from the Toys book.
My supervisor says that, although they're a rowdy bunch, they can talk more about science than any prior Conceptual Physics class at the school. I feel that they are much more open to taking on new science concepts, and work to remember the new words like Fulcrum, Mechanical Advantage, and now coil and induce. I hope they enjoy chemistry next year!