I broke my leg this year and had to go to physical therapy. One of the things they had me do was stand on a "rocker board", close my eyes, and maintain my balance. A rocker board is a small piece of wood with a curved bottom (kind of like a rocking horse). You can place it different ways so that you balance side to side, forwards and backwards, or diagonally.
Here are some places you can buy them:
http://www.bodytrends.com/ftrwobbleboard.htm
http://gymball.com/rocker_boards.html
http://kytec.spacestar.com/fitter/Fitter.html
http://www.performbetter.com/catalog...sp?dept_id=213
http://www.promedproducts.com/balance_boards.htm
http://www.fitter1.com/wb.html
I am not associated with the above sites, nor have I ever used them. I don't know how reliable they are. You might be able to find one locally or even make one.
Good luck!