Black Gold

Oil. A portfolio dominated by it bubbles when prices are up and sinks downward when they're not.

For emerging-market enthusiasts, ING's Russia Fund (LETRX) has been one of that category's top performers. Ranked No.1 in performance history in five of the past seven years by Morningstar, this fund of some 35 holdings got its high marks thanks to black gold and other resource-type stocks. (As of late August, ING's Russia Fund holdings had about 43.74 percent of assets invested in oil and gas companies.)

"We've had a very good run," says Sam Oubadia, one of the fund's portfolio managers. Oubadia is a fan of Russian equities because it's one of the largest emerging markets around, valuations are still cheap, and Russia attracts a lot of global investors. But the Russian market tends to be more volatile than your average emerging market. Oubadia warns investors to "be aware that the transparency and level of corporate governances are not the same as in developed markets."

Dian Vujovich is an author, syndicated columnist and publisher of fund-investing site www.fundfreebies.com.