There's a lot going on in the mutual fund world; if you miss something, it could end up costing you money. To keep you up-to-date, we've scoped out some of the recent happenings in the fund industry during the past week, discussed and how they may affect your portfolio.

More (nearly) free ETFs
The exchange-traded fund price war has a new combatant. TD AMERITRADE (Nasdaq: AMTD) recently announced that it would allow customers to buy and sell roughly 100 ETFs free of commissions. The list of commission-free ETFs includes funds from iShares, Vanguard, and State Street, among others. This announcement follows earlier moves by Charles Schwab (NYSE: SCHW) and Vanguard to cut or reduce commissions on their own proprietary ETFs for brokerage clients, and Fidelity's move to offer free trading on 25 iShares ETFs for its customers. Investors should expect more ETF-trading price cuts in the future, from other brokerages trying to cling to customers in what is fast becoming a race to the bottom.

While early indications suggest that free commissions haven't translated into huge gains for exchange-traded fund products just yet, I expect that inflows will begin to pick up as investors shake off their fear of the stock market and get back to the business of investing. Ultimately, free commissions are a good thing for investors -- assuming you don't abuse the privilege.

Just because you can trade ETFs for free doesn't mean you need to crank up the frequency of your trading. ETFs should be bought as long-term, buy-and-hold investments, not short-term trading vehicles. Investors should also stick to broad-market funds, and stay away from more expensive single-sector funds and leveraged ETFs. You can meet your long-term goals by investing in exchange-traded funds. Thankfully, that route now looks cheaper than ever.

Survival of the biggest
While ETFs have certainly proved popular with investors, many companies rolling out their own ETFs have encountered difficulty in turning a profit. The industry is dominated by a few big players such as Vanguard, State Street's (NYSE: STT) SPDRs, and BlackRock's (NYSE: BLK) iShares, making it harder for newcomers to carve out their own niches and actually make money.

For example, a recent Wall Street Journal article highlighted that Wisdom Tree, the only publicly traded firm that makes its business solely from its line of ETFs, has nearly $7.5 billion in net assets spread across 43 products, but collected just $10 million in revenue for the three-month period ending this June. Wisdom Tree has only recently recorded its first quarter of positive operating income since entering the business in 2006.

The result of all this competition? While 129 new ETFs have opened this year, 37 have been closed or liquidated. It's a safe bet that not every ETF in existence today will be around in another year or two, as the field gets even more crowded.

To make sure that you're not stuck holding a fund likely to be merged or liquidated out of existence, avoid gimmicky ETFs like leveraged or inverse leveraged funds. I'm still not totally sold on actively managed funds, either. Stick to funds that have a meaningful level of assets, so that you don't have to worry about potential liquidity concerns. This likely means investing in funds that have been around for several years, not in trendy, more expensive new ETFs that track obscure benchmarks and don't have a performance track record.

Expenses are a decent indicator of a fund's suitability for most investors. The lower the cost, the more simple and well-diversified the fund usually is. Low prices typically mean you're getting frills-free broad market exposure -- exactly why you should be buying ETFs in the first place.

A loss for the fund world
The mutual fund business lost a great investor this past weekend, when Hakan Castegren of Northern Cross Investments passed away at 75. Castegren was the lead portfolio manager of the Harbor International Fund (HIINX), one of the top-ranked foreign funds around. Over the past 15 years, the fund has outranked 96% of all foreign large-blend funds; Castegren's death is clearly a loss for the fund.

Despite Castegren's death, the fund has not been left completely in the lurch. A team of four other portfolio managers from Northern Cross joined Castegren in February 2009. They had supporting Harbor International for many years before formally joining the fund. 

The fund invests in foreign developed- and emerging-market companies that management believes have serious growth catalysts set to materialize in the next few years. Industry leaders like Brazil's Petroleo Brasileiro (NYSE: PBR) and Banco Bradesco (NYSE: BBD), as well as Belgium's Anheuser-Busch InBev (NYSE: BUD), illustrate these managers' approach toward choosing promising investments.

While it's reassuring that the fund will have some continuity, I'd recommend that investors hold off on investing new money here. Current fundholders shouldn't feel the need to sell just yet, but I'd keep a careful eye on any changes that may occur in the portfolio now that Castegren's gone.

Although the new team of portfolio managers has a prior history of indirectly supporting the fund, and roughly 20 months of direct involvement, I'd prefer to see some longer-term live results under the new team before I pass a final judgment. I do hope the current team continues in its winning ways, because this truly is one of the better foreign funds in existence. I'd like nothing more than to continue to strongly recommend the fund to investors.

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Amanda Kish is the Fool's resident fund advisor for the Rule Your Retirement investment newsletter. At the time of publication, she did not own any of the funds or companies mentioned herein. BlackRock is a Motley Fool Inside Value pick. Charles Schwab is a Motley Fool Stock Advisor choice. Petroleo Brasileiro is a Motley Fool Income Investor recommendation. Try any of our Foolish newsletter services free for 30 days. The Motley Fool has a disclosure policy.