Gold, gold, gold - It is a play on the American dollar and currency that is leveraged to the dollar, as well as a play on American stability. We have seen new demand in the past four years that has been somewhat unique in the history of gold spot trading, and this has also given gold its upward momentum.
TIPS - Treasury Inflation Protected Securities. These pay a variable premium in addition to the current rate of inflation...so if inflation is 4 percent, and the current TIPS premium is .75 percent, you will get a 'coupon' of 4.75%. Bond markets are heavily tied to interest rates, so this is one bond that will generally do well during periods of stagflation or increased inflation.
Global Investing - Emerging markets tend to do well in times of American floundering. Investing in Latin America or Russia over the past five years, for example, has led to returns for some of nearly 50% a year on average.
Commodities - Commodities are a great way to offset US equity holdings. Gold, Steel, Copper, and Oil very much tends to zig when American markets zag, and a stagflation situation would be no different. This is also a time, historically, when commodities tend to do very well, although in my opinion most commodity prices at this point are quite high.