Every month, I identify a few companies that I think are worthy of my own investment dollars. My lump-sum retirement and growth portfolios are both performing spectacularly well, but the same hasn't been the case for my monthly Roth contributions.

This will mark the 12th month of my public picks, and on the year, my investments haven't gained -- or lost -- anything. I believe this month's picks will help reverse that trend. Read ahead and you'll see why, and at the end I'll offer you access to our newest special free report.

Baidu (Nasdaq: BIDU)
China's leading search engine was actually my pick just over a month ago. Since then, the company came out with a stellar earnings report that only reinforces my initial reasons for buying. I've already done a larger article on Baidu's latest news here, but here's the key part:

The most important numbers -- other than impressive 60% increase in revenues -- come from a strengthening core business with a commitment to keep innovating. The company increased its list of online marketing customers -- the main source of revenue -- by 18% over the same time last year. Just as important, each customer was contributing 35% more revenue than it was last year. The advertising proposition Baidu offers clearly works, or advertisers wouldn't be willing to continue paying more for its service.

Though some on Wall Street may decry the fact that research and development costs increased by 83% -- outpacing the revenue increase -- I think this is a good sign for the company's future. Baidu needs to spend money on top talent if it wants to stay ahead of the game. China's Internet marketplace is just taking shape, and Baidu has an enormous opportunity to solidify search, mobile, and cloud services.

Intuitive Surgical (Nasdaq: ISRG)
Investors in the medical sector could be forgiven if they looked at Intuitive's 16% drop since early May and thought the company might be going the way of MAKO Surgical (Nasdaq: MAKO) -- which has suffered setback after setback in the past few months.

After reading through the company's quarterly earnings release, I can solidly state that that isn't the case. Revenue was up 26% for the maker of the da Vinci Robotic Surgical System, and earnings were up 30%. At the same time, operating expenses were only up a paltry 16%.

The only dings for the company came from weakness expected in Europe and a rise in the cost of products sold. Eventually, the crisis in Europe will work itself out, and parting ways with Intuitive because of it would be silly. And the input costs were higher because the company was introducing a bevy of new products for hospitals to try at discounted prices. I think that's a great long-term move.

But there are two numbers that speak volumes about how safe an investment in Intuitive is: 26% and 58%. In the second quarter of 2012, the number of procedures carried out with da Vinci grew by 26% even though there were fewer prostatectomies performed in the United States than expected. And recurring revenue now makes up 58% of all revenue for the company -- that's a solid stream of cash!

And it's trading at just over 29 times free cash flow. That's not a low number, but I think it's more than fair for a company like Intuitive Surgical.

Cummins (NYSE: CMI)
Finally, we have one of the nation's leading engine makers. Before its earnings release this past Tuesday, Cummins' shares were down about 30% from their mid-March highs. This was primarily due to worries about slowed demand from both China and Brazil. Earnings revealed that those concerns were well founded, but solid demand from North American companies helped offset these weaknesses.

As it stands, Cummins is one of the leaders in producing engines that will meet high-standard emissions tests. This could be important moving forward, as more people will be worried about reducing pollution. The company is also on the cutting edge of natural gas engines -- first through its partnership with Westport Innovations (Nasdaq: WPRT), and now through its attempt to build a 15-liter natural gas engine of its own.

Want more details on Baidu and MAKO? Don't worry -- The Motley Fool has you covered with our premium research reports. You can find our recommendations for how to play Baidu in this premium research report, and for MAKO in its own brand-new premium report. In each report, you'll find everything you need to know about the company, including whether it's a buy at today's prices. Click here for instant access to information about Baidu. To get started with info about MAKO, click here now.