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

Targeting retirement
Investors haven't exactly been enamored of actively managed mutual funds in recent years, but there is one area of the market that has been on an upswing: target-date funds. These funds offer a one-stop shop for investors looking to create a diversified portfolio all at once, by investing in several underlying funds from the same fund family. And according to a new study by the Employee Benefit Research Institute and the Investment Company Institute, investors are increasing their use of these funds to meet their retirement goals. Nearly 10% of assets in 401(k) plans tracked in the companies' database are now invested in target-date funds, while fully one-third of plan participants hold such a fund.

While target-date funds aren't for everyone, investors who want a little bit of help with their asset allocation decisions should take a second look. And if your 401(k) or other retirement plan doesn't have a lot of good asset class-based options, a target-date fund may make more sense.

However, there are a few things to keep in mind when considering these investments. First and foremost, make sure you understand how your fund is investing and how aggressive your equity allocation is. Equity exposure varies widely across fund families, even for funds with the same target retirement date. Secondly, make sure your fund shop isn't "double-dipping" with respect to fees. In other words, make sure you're not paying fees on both the target-date fund itself and on the underlying mutual funds. While many fund companies do charge two layers of fees, there are some notable exceptions including Vanguard, Fidelity, and T. Rowe Price, so put these fund families at the top of your list when shopping for target-date funds.

Investigation under way
It seems that mutual fund investors were barely able to recover from the market timing and illegal late-trading scandals of 2003 before the bear market of 2008 hit. And just when we thought we were getting our bearings again, it looks like another insider trading investigation is under way. The FBI recently searched the offices of several hedge funds during the investigation, and last week, the mutual fund world was drawn into the fray. A number of fund companies received informational requests from federal investigators last week, including big-name shops Janus Capital Group (NYSE: JNS) and Wellington Management. It's too soon to tell whether these initial requests will lead to further scrutiny for Janus and Wellington or whether other fund firms will be added to the list of affected companies.

While no investors want to hear that their fund company may be even peripherally involved in an insider trading investigation, make sure you don't jump the gun here. Just because a fund shop has been contacted by authorities in the course of an investigation doesn't mean that the company is guilty of wrongdoing. So if you own any funds that are directly managed or subadvised by Janus or Wellington, don't panic and jump ship. The situation definitely bears closer watching, but it's too early to make any definitive calls. Sit tight for now and pay close attention to how the investigation unfolds before taking any action.

Signaling value ahead
In more positive fund news, Vanguard continues to lead industry efforts to cut mutual fund fees for retail clients. Vanguard recently announced that it would eliminate the high investment minimums for its Signal Share class, which is used most often by financial advisors and institutional investors. The Signal Shares, available for roughly 25 of Vanguard's index funds, offer very low annual expenses, but the $1 million to $5 million minimum kept many out of the funds. With the elimination of these minimums, many new investors will now be able to take advantage of this low-cost share class, which runs as low as 0.07% in some instances.

If you're an index fund advocate, this move should be music to your ears. Be sure to look out for freshly discounted Signal Shares in places like a retirement plan. And keep in mind that Vanguard also offers an ETF version of many of its index funds, so you've got some options here. For example, the Vanguard Emerging Markets Stock Index Signal Shares (VERSX) comes with a low 0.27% price tag, but you can also buy Vanguard Emerging Markets Stock ETF (NYSE: VWO) for the same price. Other highly recommended Signal Share funds that are available for the same cost in an ETF format include Vanguard Total Stock Market ETF (NYSE: VTI), Vanguard Total Bond Market ETF (NYSE: BND), Vanguard European ETF (NYSE: VGK), and Vanguard Small-Cap Index (NYSE: VB). Whether you prefer index funds or exchange-traded funds, Vanguard's got the goods for investors who want to track the market at the lowest possible cost.

Making the right moves with your mutual funds is just one key toward a successful retirement. Click here to read the Fool's new special report, "The 7 Secrets to Salvage Your Retirement Today."

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. The Fool owns shares of Vanguard Emerging Markets Stock ETF. Try any of our Foolish newsletter services free for 30 days.

We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.