Even cash isn't safe anymore. The U.S. dollar index, which compares the greenback to the world's major currencies, has fallen about 15% this year and is near its lowest levels ever. Recession fears are driving the dollar lower, as jobs disappear, home prices fall and consumer confidence plummets.
And the Federal Reserve isn't helping out. The market is betting the Fed will lower interest rates by 50 to 75 basis points at its meeting next week. That lowers the yield on the dollar versus other currencies, helping grease the skids to send it even lower.
In short, even if you put all your money in cash, and then put that cash under your mattress, you'll still lose money.