Simple lesson to review simple machines. It's tagged for 3rd - 5th grade, but could work for a quick review. It has a card sort activity ready to go. The agricultural examples might not be 100% relevant to all kids, but still useful.
The emerging set of interactive simulations at PhET that now use HTML5 and work solely within a modern browser. These are heavy in the physical sciences... but also include acid-base, atomic structure, chemical equations, etc.
Use a two liter, three pencils, vinegar, baking soda, a paper towel, and a cork to build this rocket. Pretty simple! This experiment easily goes along with Newton's Laws, scientific inquiry, or chemical reactions.
i tried this demo for the first time this year. It didn't work perfectly but it really gave the students a visual of the formation of minerals. I would suggest marking the water level on the jar when you first set it up so they can really grasp how much has evaporated by the end. I let mine sit for almost 3 weeks but crystals were forming within 3 days.