In One Up on Wall Street, Peter Lynch tells us that the size of a company matters a lot when considering how much upside you can expect. He notes that "big companies don't have big stock moves" and advises that investors will "do better with smaller companies."

In order to find outstanding performers for our "10-Bagger Portfolio," we're hunting among some of the best small companies we can identify right now. Below are seven tremendous small-cap businesses that we're taking a particularly close look at right now. Here are brief summaries on why we like each of them:

1. Pandora (NYSE: P). If you think Pandora is just a gimmick, think again. The online music company is going after the big prize: radio's advertising dollars. And as the world becomes more connected, the cash will begin to flow. With a market cap of just under $2 billion, this one has plenty of potential upside.

2. Greenway Medical. Greenway Medical supplies management software to urgent care centers, which are popping up all over the place. The company looks like a nice way to play emerging health care trends. This one has a market cap under $500 million, so we're fine taking our time getting to know the business.

3. Nuance Communications (Nasdaq: NUAN). Nuance is perfectly positioned within the growing mobile computing trend. Over time, its voice recognition software could send your keyboard into the same closet as your Nordic Track device. With its market cap of over $7 billion, Nuance is no longer a small-cap, but we think it has a lot of growth ahead of it nonetheless.

4. Jive Software. Nowadays, the business world is all about collaboration. Jive Software has actually created a technology platform using social communication tools to help workers collaborate -- and it's signing up customers at a rapid pace. Sure, the company's name is somewhat cloying, but this $1 billion company appears to have a very bright future.

5. Bazaarvoice (Nasdaq: BV). Bazaarvoice helps companies get the most out of their online data. And that's becoming increasingly important. Without a strong online presence, traditional retailers are going to be left behind. At roughly $1 billion in market cap, Bazaarvoice has plenty of headroom.

6. Enphase Energy (Nasdaq: ENPH). Solar panels can't help customers without an inverter turning DC power outputs into AC power that people can use. Recently, more and more people have been substituting central inverters for Enphase's microinverters. If that trend continues, investors in Enphase will benefit handsomely. At under $250 million in market cap, this one is very small -- so we're happy to watch this one for a while.

7. Zynga (Nasdaq: ZNGA). Many people think social gaming is just a flash in the pan. With millions and millions of monthly average users, that claim doesn't hold much water, in our humble opinion. Zynga is leading the charge when it comes to mobile gaming, and its bringing a new generation of gamers with it. Now at $4 billion in market cap, Zynga's share price is down considerably from its highs. We think this one might be worth a second look by skeptical investors.

One more for the road
Fool co-founder David Gardner has identified another company that has multibagger potential. At $1 billion in market cap, it has considerable upside. And it's also poised to benefit from long-term trends in the rapidly growing health care sector.

To learn more about this small-cap company that is disrupting its industry, have a look at our free report called "Discovering the Next Rule-Breaking Multibagger." This has been one of our most popular free reports to date -- and you can grab your copy right now by clicking here.