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

Living Dead Booksellers
Browsing the "investing" section of your local bookstore can be very educational. Especially if it's OK to plop down and read without buying the book. This week, there was a valuable investing lesson to be learned in the "bookstore" section of your local stock market.

Fool writer Alyce Lomax highlighted how shares of Barnes & Noble (NYSE: BKS) spiked more than 20% Wednesday, on word that the company was putting itself up for sale.

Buyouts can benefit shareholders, as when Disney bought Marvel in 2009. But investors shouldn't count on a rich exit, especially not for a bookseller nowadays. Alyce noted digital competition from companies like Amazon.com (Nasdaq: AMZN) and discount competition from big-box stores like Target (NYSE: TGT) and Costco.

"Big bookstores are perfectly fine places to pick up horror stories from the likes of [H.P.] Lovecraft. But big bookstore stocks could fill your portfolio with soul-curdling horror," wrote Alyce.

BP Is History; Oil Is the Future
Fool analyst Nate Weisshaar went beyond the headlines to help investors figure out what's going on in the world of oil and what it indicates for overall economic health.

"Let's assume there is a correlation between oil prices and economic activity," wrote Nate. If oil prices are expected to remain strong, oil companies will spend money to get crude out of the ground. So it makes sense to look at what's happening with the companies that help Big Oil companies like BP (NYSE: BP) and ExxonMobil (NYSE: XOM).

Click to the article for Nate's analysis of three companies, including CGG Veritas (NYSE: CGV), which uses seismic technology to help oil companies figure out where to drill.

Are Penny Stocks Really That Good?
If you're just starting out in investing, buying cheaply priced stocks might seem like a good idea because you won't have to spend too much to get a lot of shares and a tiny bump in share price could bring you a tidy return.

But penny stocks usually are bad for your financial health. "The point is, if they're not outright scams then they're little more than shell companies with a business plan," wrote Fool Rich Duprey. "Indeed, most probably don't have revenues or even a product. It's forever under development, and only by raising more money by issuing shares will they survive."

Click to the article to learn more about tempering your risk by understanding the companies behind the penny stocks.

Costco Wholesale and Walt Disney are Motley Fool Inside Value picks. Amazon.com, Costco Wholesale, and Walt Disney are Motley Fool Stock Advisor recommendations. CGG Veritas is a Motley Fool Global Gains selection.

Fool online editor Kris Eddy doesn't own shares of any stocks mentioned in this article. Try any of our investing newsletters free for 30 days. The Motley Fool has a disclosure policy.