I made this display at Techshop SF, visit their website here: http://techshop.ws/
Step 1: Necessary Components
-Strong neodynium magnet
-Light lubricating machine oil (any oil will do)
-MICR, a.k.a. magnetic ink. I ordered this online for about $10. Try searching ebay for magnetic toner refill.
Total, the components cost around $25.
Step 2: Make the Ferrofluid
Use the stir stick to ensure the oil and ink are well mixed.
Step 3: Mix the Ferrofliud and Water Into the Jar
This is the finished product! I like to shake the jar up so there are little suspended blobs of ferrofluid, and then bring the magnet to the side of the jar. The blobs race to magnets and converge into one mass that you can move around using the magnet.