How to Play The S&P By Revenues

S&P 500 companies have seen big changes in their market caps. Maybe it makes more sense to play them by their revenues -- and now you can, via a new ETF.

In this installment of ETF 101, CNBC's weekly "lesson" on exchange-traded funds, Mary Thompson reports that RevenueShares Investor Services is offering a new ETF, with weightings based on revenues instead of capitalization: the RevenueShares Financials Sector Fund.

The new ETF joins the firm's already existent RevenueShares Large Cap ETF, which competes with the market-cap-weighted iShares S&P 500 Index.

Top ETFs:

- SPDR Gold Shares

- Ultra Oil & Gas ProShares