Fools were out and about this week in an investing world jampacked with actions and ideas. Here are three articles you might find useful as you decide how to invest your money.

The Nasdaq-100 Gets a Facelift
Fool contributor Sean Williams advises investors not to get too caught up in the reweighting of companies within the Nasdaq 100. "Keep your eyes on the long term and ignore the mutual fund white noise over the next month," Sean advises.

Among the 18 companies whose share of the index will rise are Microsoft (Nasdaq: MSFT), Oracle (Nasdaq: ORCL), Intel (Nasdaq: INTC), and Google (Nasdaq: GOOG). Apple (Nasdaq: AAPL) will lose share but will retain the largest weighting, at 12.3% of the index.

Shareholders of companies within the index -- which is made up of 100 of the largest domestic and international nonfinancial securities, based on market capitalization -- may see a "buying or selling flurry from mutual funds and hedge funds which closely track the index," Sean writes. But he also tells us that it's more important to pay attention to the earnings reports the companies are presenting.

Check out the article for more on the Nasdaq-100's facelift.

Should You Buy These Fast Growers?
Foolish fund expert Amanda Kish dived in to help investors decide whether to invest in any of the
10 fastest-growing small and midsized mutual fund companies of the past five years. The fund shops in the list from research firm Strategic Insight are "clearly doing something right, capturing inflows and growing assets in a notoriously difficult market," Amanda wrote, but she went far beyond that point to help investors understand the whole story.

Her analysis included looking at investment strategies, stock holdings, returns, and fees. Follow the links for part 1, part 2, and part 3 of Amanda's research on all 10 companies

Is Berkshire Built to Last?
Fools admire Warren Buffett (a lot), so you might be surprised at the answers this week from Motley Fool co-founder Tom Gardner, Motley Fool Inside Value advisor Joe Magyer, and Motley Fool Global Gains advisor Tim Hanson on whether Berkshire Hathaway (NYSE: BRK-B) is built to last and whether it will succeed after Buffett's gone.

Here are a few tidbits:

  • Tom: "[W]hile serious investors would do well to study Buffett every single day, I have a concern with Berkshire. I don't see enough indication that there is a system of internal learning in the culture."
  • Tim: "Although the company's myriad operating assets are strong enough to keep it treading water, this is such a Buffett-centric company -- regardless of what he writes in his annual letters."
  • Joe: "Buffett has done a tremendous amount of succession planning via Berkshire's checkbook. His major investments in wide-moat, long-lived businesses like railroads and regulated utilities have cemented Berkshire's staying power."

Read the article to see the full discussion, and join in using the comments box on that page.

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Fool online editor Kris Eddy owns no shares of any stocks mentioned in this article.

Berkshire Hathaway, Google, Intel, and Microsoft are Motley Fool Inside Value picks. Google is a Motley Fool Rule Breakers choice. Apple and Berkshire Hathaway are Motley Fool Stock Advisor recommendations. Motley Fool Options has recommended a bull call spread position on Apple and diagonal call positions on Intel and Microsoft. The Fool has written puts on Apple, has bought calls on Intel, and owns shares of Apple, Berkshire Hathaway, Google, Intel, Microsoft, and Oracle. Motley Fool Alpha LLC owns shares of Microsoft. Try any of our Foolish newsletter services free for 30 days. We Fools don't 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.