I did this experiment in my science class while I was in middle school:
Fill a glass with water and then put a piece of cardboard on top of it and then slowly turn the cup upside down and ta-da, the cardboard will be able to hold the water from leaking out. Okay, empty the glass and then do the same thing again, but this time, poke a small hole in the center of the cardboard and try to flip the glass around... this time, the water get spilled out all over because the pressure inside the glass is able to interact with the pressure outside the glass, thus there's no pressure force to hold the water from falling down due to the force of gravity.
Thank you for using the Jiskha Homework Help Forum. The suggestion looks easy, although you could drip water where you don't want it! Here are some ideas for a Science Fair, etc.:
2. (part II of #1): http://www.terimore.com/
3. (more ideas): http://classroom.all-science-fair-projects.com/forum/showthread.php?t=215
4. (part II of #3): (oops, looks identical): http://classroom.all-science-fair-projects.com/forum/showthread.php?t=187
There are still more sites out there but these look like they'll be enough.