Here’s an R/C hovercraft toy made mainly out of junkbox parts:

The workings of a hovercraft are fairly straightforward: one high-power motor with an airplane propeller forces air down through the hole in the center, which pushes the bottom of the hovercraft off the ground. This greatly reduces friction, allowing the hovercraft to scoot around without much trouble. It also makes it much more difficult to control, however: when the hovercraft turns, it will keep traveling in a straight line unless more thrust is applied. Since we are used to controlling cars or boats, the newtonian behavior of a hovercraft is challenging indeed. The body of the hovercraft is made out of styrofoam, cut with a saw and sanded to smooth the edges. The skirt on the bottom is made out of pieces of a plastic GAP bag, attached with Scotch tape and hot glue. The radio control unit was scavenged from an old boat I had, along with the drive motor mounted on the wooden supports, while the lifting motor was from my physics teacher. The battery is 300 mAh 6V NiMH (or NiCd, I forget), and I have a pair of them. They were about $6-$10 each (again, forgot) and about $12 for the 2 1/2 hour charger. The servomotor for steering was from an old RC car I had

Project Hovercraft [via Hacked Gadgets]

More:

• DIY Hovercraft with 4 PC fans @ 22V!
• Garage Hack: Hovercraft
• Thirty minute hovercraft
• Homemade Hovercraft Instructions – Weekend Projects