Groovy Lava Lamp
This project is all about oil and water not mixing. Basically you take a bottle and fill it about 2/3rd of the way with water then fill the rest with water that has some food coloring in it. Then to actually make the lava effect, you put little pieces of alka-seltzer in the water and it bubbles and makes the water rise through the oil. It didn't work very well, but it was fun to do. The bubble didn't last very long and the alka-seltzer kept floating to the top.
Marshmallow Catapult
Making the marshmallow catapult was also pretty fun, but with mixed results. One of the problems with this one is that the instructions were really vague and didn't give enough detailed information so we had to guess a little bit. It was pretty fun to make and I think that if we made a Marshmallow catapult 2.0 it would be much more successful.
CD Hovercraft
http://familyfun.go.com/crafts/crafts-by-type/educational-craft-activities/science-projects/ride-on-a-hovercraft-847787/
The CD hovercraft was also somewhat less than successful. It kind of worked, but the wooden spools that I bought were too small and the balloons kept coming off. I got some bigger spools to try again, but the first version was not very good. Hopefully the next round will be more successful.
Duct Tape Fun -
Our most successful craft came from making stuff out of Duct Tape. I must admit, that I was quite impressed that my daughter did most of this on her own. She wanted to make a bag, and so I said go for it. I helped her start the sides of the bag after she made the bottom, but she did most of the bag by herself (including straps and a pocket). She spent almost the whole weekend playing and making stuff out of two roles of duct tape. I couldn't help but feel so proud of her for being so creative.
Finally we did the nice Mentos and coke experiment, just for fun.
It was really fun to spend some time with my kid, and she loved having some attention from her dad that tries to play with her, but doesn't always do a good job of it. It was neat to teach her some actual scientific information about how some of these things work, and I hope that more of this DIY movement continues to spread.