Exchange-traded funds have been one of the fastest-growing corners of the fund business, grabbing roughly $1 for every $2 that flowed into conventional long-term mutual funds in 2010. But it's not just fund companies that are sniffing opportunity.

Media and research firms from Standard & Poor's to IndexUniverse are competing to be the chief supplier of information to ETF investors, much the way Chicago-based Morningstar won over mutual-fund investors a generation ago. Amid the scramble, competitors including Morningstar itself have launched a slew of online tools, many of them free, such as rankings and search engines that help compare the hundreds of ETFs available.