[Note: We're happy to announce that today's column is written by a Foolish Drip community member, Paul Litvak.]

How can an investor build a diversified portfolio with a reasonable amount of stocks?

In his book Common Stocks and Uncommon Profits, legendary investor Philip A. Fisher stated that a large amount of diversification can be found even when investing in a small handful companies.

That's because diversity is found not only by owning stocks in several companies, but by owning companies with diverse product lines. Let's look at a few companies with several revenue streams. (The following are examples only -- they're not recommendations.)

Want diversity in the technology field? Try Intel (Nasdaq: INTC). According to Intel's 10-Q, the company's products include microprocessors, chipsets, systems management software, conferencing products, digital imaging products, graphics products, flash memory products, embedded processors and microcontrollers, and network and communication products (it has also begun to offer large data server services).

Since Intel has a strong financial position, it is also able to purchase other companies. Finally, Intel has one of the largest investment portfolios in the technology world, providing additional diversity. A vast majority of Intel's revenue is still earned from microprocessors, but the company is hard at work adding new revenue streams. Intel's dividend reinvestment plan is fee-free; however, ownership of one share is required before you can join.

How about a company in the energy field? Take a look at Exxon Mobil (NYSE: XOM). The Exxon Mobil shareholder prospectus states that the company deals in natural gas, crude oil, petrochemicals, petroleum and specialty products, copper, coal and other minerals, and the generating of electric power. The investment plan is fee-free and the investor can start with the company's plan directly.

Consumer products? Easy. Take a look at Procter & Gamble (NYSE: PG). The company has five main areas: healthcare, paper, food and beverage, beauty care, and laundry and cleaning. Healthcare products include Crest, Metamucil, Nyquil/Dayquil, Pepto-Bismol, and Scope. Paper products are Tempo, Puffs, Charmin, Bounty, Always, Tampax, Luvs, and Pampers. Food and beverage products include Jif, Crisco, Folgers, Pringles, and Sunny Delight. (Making me hungry already!) Beauty care includes Ivory, Safeguard, Zest, Cover Girl, Head and Shoulders, and Vidal Sassoon. In the laundry and cleaning business, we find Tide, Mr. Clean, Cheer, Dawn, Cascade, Bounce, Downy, and Joy. The company also produces other items not listed here. An investor can contact the company directly to start the investment plan; however, fees are involved.

Need a conglomerate? What about Minnesota Mining and Manufacturing (NYSE: MMM)? 3M, for short, markets major automotive parts, medical devices, office supplies, and telecommunication and electrical products. The company also markets and manufactures specialty chemicals, abrasives, and adhesive tapes. Ownership of one share is required for admission to the investment plan, which is free of fees.

Want something in the leisure field? You could ride Harley-Davidson (NYSE: HDI) down that road. The company makes and sells motorcycles (Harley Davidson and Buell), is involved with mechanical and cosmetic accessories, replacement parts, consumer goodies such as toys, jewelry, T-shirts, small leather items, and other products. The company also has a credit and insurance group. Again, one share is required for admission to the plan, which is fee-free.

Now for the disclaimer: This writer holds direct investment positions in Intel, Exxon Mobil, and Procter & Gamble. Certainly there are many other companies that would qualify for this article as being diversified businesses. The number of stocks chosen for your portfolio are, of course, your decision. Merely look around, do your due diligence, and choose Foolishly!

[P.S. To discuss this column and direct investing, meet on the Drip Companies message board linked below!]