Here’s a list of some Exchange Traded Funds that you can use to trade commodities, such as gold, the US dollar, oil, etc.
US Dollar: UUP
Oil: USO, Others here
Natural Gas: UNG
Gold: GLD, AU, GOLD
Silver: SLV
Bonds: TLT (20 year bonds), Others here
Nasdaq: QQQ
DOW: DIA
SP500: SPY
Russell 2000: IWM
Entire US Stock Market ETF: VTI
ETFs for currencies: go here
Forex Options: Go Here for Info