Last week I wrote an article cheering the virtues of diversification. To be sure, it is a noble pursuit and one that we should all strive to achieve. Why? Diversification can protect us from the sometimes uber-moody Mr. Market. Spreading our capital among different companies of different sizes in different sectors can lead us to some excellent returns without taking exceptional risk. In that light, I offer you three more stocks for a diversified portfolio.

Large cap
There is no doubt that the Gulf oil spill and BP's exposure to the whole mess has scared a lot of people away from the energy sector. To be sure, no one can really say what will become of it all. However, I do believe that as long as there's oil in the ground there’s going to be companies searching for and producing it. Enter oil industry giant ExxonMobil (NYSE: XOM).

As polarizing as oil is today, you cannot deny the strength and competitive advantages this company possesses. With a net cash position of $4.4 billion and a market cap of around $275 billion, Exxon is one of the biggest companies out there. Some may argue this gives it more room to fall. That's possible, but given BP's current situation and Exxon’s tremendous net cash advantage over fellow competitor ConocoPhillips (NYSE: COP), I like Exxon as an energy play. Trading around $59 and sporting a yield of 3%, Exxon looks pretty attractive right now.

Mid cap
It keeps going and going, and Energizer Holdings (NYSE: ENR) is about more than just batteries. This mid-sized company sees some pretty stiff competition from its Goliath, Procter & Gamble (NYSE: PG). But in the market for everything from batteries to baby care, there is enough room for both companies to do well, and Energizer is holding its own. One of the qualities that makes this business so attractive is that it sells well-known disposable brand-name items; names like Schick, Edge, Playtex, Hawaiian Tropic, and yes, even Energizer.

The operative word here is disposable -- as in recurring sales, which I really like. True, the company does quite a bit of business with Wal-Mart (NYSE: WMT) to the tune of approximately 21%. Normally, so much exposure to one customer would concern me. But this is Wal-Mart we are talking about, so my concerns are somewhat mitigated. Also, nearly half of the company's revenues in 2009 came from international operations. Trading at just seven times free cash flow, Energizer should keep your portfolio going and going for some time to come.

Small cap
Ahh, pizza. Is there anything it can’t do? Not only is it one of nature'’s greatest creations, but now it looks like it may help create a little wealth as well. Papa John's (Nasdaq: PZZA) is one of those companies I have been looking at for a while, and I think now is an excellent time to fire it up. Competition in the market is fierce for sure, as Papa John's goes toe-to-toe with the likes of Domino's Pizza and Yum! Brands' (NYSE: YUM) Pizza Hut.

But the Papa is gaining market share where its competitors seem to be losing it. Since 2005, Papa John's share has risen from 10.5% to 11%, while Pizza Hut and Domino's have both lost between 1.5 and 2 percentage points. More share means more pies, and Papa John's is outperforming its peers in customer satisfaction as well. Better ingredients and better pizza translate nicely as the company continues to expand overseas into places like China and the Dominican Republic, and I look for this to continue to add to the bottom line. With only a $670 million market cap, the Papa has some room to grow. With a healthy balance sheet and shares trading at just 11.5 times free cash flow, Papa John's may just deliver some supreme gains straight to your portfolio.

Again, I cannot emphasize enough that these are ideas meant for further research and not formal recommendations. However, with these three companies you get a different slice of the market: a big oil play, a purveyor of many well-known consumer brands, and pizza (need I say more?). Three companies that may just help you realize your destiny with diversity.

Energizer Holdings and Wal-Mart are Motley Fool Inside Value recommendations. Energizer Holdings is a Motley Fool Stock Advisor selection. Motley Fool Options has recommended a bull call spread position on Yum! Brands. The Fool owns shares of Procter & Gamble, which is a Motley Fool Income Investor selection.