Solution 1: For flash dances out on the streets of Ashland, Bjorg uses a painter’s tarp and duck tapes down the edges. Works pretty well!
Solution 2: Buying a large piece of linoleum or vinyl from a home store is cheap and easy to lay down, but if on concrete there’s no padding and I found that the edges curl up pretty badly.
Solution 3: Dance Deck (and other companies–try a Google search) make 1 ft sq vinyl tiles that snap together easily and can be laid over concrete or smooth lawns. Each tile weighs 2 lbs and costs about $5 per tile. I bought 225 pieces for my pool deck from Sports Products Plus and was happy with their service.
Solution 4: These days most hotels have carpeted ballrooms and covering a large area for re-occurring festivals can be a challenge. Nancy and George, who organize the San Miguel Festival in Mexico, came up with a clever solution. They bought vinyl simulated wood flooring (like Pergo that one normally installs permanently in a home or apartment) and laid this over the carpet with extra wide duct tape around the edges to hold the system in place. Cost for these floors is typically $1-$5/sq ft. Quality of the results for dancing is excellent. However, the floor does not easily go over bumps and great care must be used in installing and removing the floor as the locking mechanism are delicate and can easily be broken.
Solution 5: Several small companies specialize in traveling to festivals and installing portable dance floors. I use and am very happy with Dance Floors of Las Vegas who install about 7000 sq ft for my Portland ValenTango Festival. (In addition, the DoubleTree contributes another 1000 sq ft for one of the classroom). Cost is about $1/sq ft.