Inventing Lego spinning tops: [These were actually really neat. They are reversible so they can be spun from either side and have different colors on the corners so they make great patterns as they spin.]
Creating mining machines for a space mission:
Making a balance from yoghurt cups and a ruler:
Writing miniature graphic novels about explorers in the jungle:
I have to confess that not one of these projects was actually a planned part of our homeschool week... these were things the boys worked on in their spare time... For us that is part of the beauty of homeschooling -- the boys have hours of free time so they are forced to come up with all sorts of creative activities to keep themselves busy ('cause mom isn't about to entertain them -- if you come tell me you are bored I can find something for you to do... dishes, laundry, sweeping...).