Image source: John Deere. 

With all of the attention internet and technology stocks get these days, companies that actually make things aren't getting much love from the market. Manufacturing stocks seem to be out of favor, but that presents an opportunity for investors.

When looking at earnings, growth potential, valuation, and dividends I found four manufacturing stocks I think are undervalued today.

Undervalued farm manufacturer
Deere & Co. (NYSE:DE) makes some of the most iconic farm and mining equipment in the world, and it plays an indispensable role in creating the food we eat.

This is a cyclical business that ebbs and flows with the economy and mineral prices. Farmers will buy equipment when times are good and pinch pennies when they're not, as will mineral miners, which can wreak havoc on earnings from quarter to quarter. But only a small handful of companies even compete with Deere in most of its markets, so over the long term the company can charge enough to make a hefty profit.

Right now, the stock is fairly cheap at 13 times trailing earnings and yielding 2.5% from its dividend.

The steady chip manufacturer worth buying
The chip business is highly competitive, and one of the best ways to stay ahead of competitors is by developing your own technology. This has always been one of Intel's (NASDAQ:INTC) greatest strengths, and it continues today.

Intel has huge market share in PCs and servers, and its investment throughout the recession in next-generation manufacturing led to its 14-nanometer products and systems on a chip. By developing the manufacturing for such products, Intel can maintain a technology lead, giving the company high margins and strong profits over the long term. At 14.7 times trailing earnings and with a 2.8% dividend yield this stock is a good deal for investors, too.

Post-it Note Flags took a number of manufacturing innovations to produce. Image: The Motley Fool.

The forgotten manufacturing company
3M's (NYSE:MMM) original name was Minnesota Mining and Manufacturing, but it has long been known by its shortened name. At its core, though, the company is still a manufacturing company, making everything from Post-it Notes to Scotch Tape in-house.

The manufacturing prowess doesn't just allow 3M to make strong margins by developing scale and technology that competitors can't copy. It also is a key part of the innovation process. 3M's film manufacturing processes play a key role in modifying and improving current products while creating a foundation for new goods. If 3M wasn't manufacturing adhesives to make tape, the Post-it Note wouldn't have happened; and if it weren't making graphics films it might not have stumbled into making brightness-enhancing films that are probably in the device you're using to read this article.

3M isn't as cheap as the two stocks I've talked about so far at 21 time trailing earnings, but it has picked up organic growth recently and a 2.5% dividend yield is among the safest on the market. 

Residential rooftop solar system. Image: SunPower.

Let the sun shine on this stock
The solar industry is finally turning a corner to long-term global viability, and no other company can match the manufacturing expertise SunPower (NASDAQ:SPWR) has built in the business. SunPower makes a solar cell that is fundamentally different from other manufacturers' and has the industry's highest efficiency at 21.5%.

SunPower is also in high growth mode, planning to triple capacity between 2014 and 2019. Combined with a planned yieldco that will allow for long-term profit from projects it builds, SunPower is just starting to show the value it can create for investors.

SunPower trades at 27 times earnings today, but that's misleading because in anticipation of the yieldco it is stashing projects on its balance sheet instead of selling them, as it has done in the past. Once the yieldco and expansion plans come to fruition I think this will be one of the best values on the market in a booming solar industry.

Value to be found in manufacturing
These are four stocks that I think present great value for investors in manufacturing. They each have competitive advantage that will keep them in front of the market, and from a financial perspective they're providing great value and dividends as well. That's a recipe for long-term success on the stock market.