From technology and media to sustainability and health care, the year's Most Innovative Companies spans a diverse range of fields. Here are the companies that made it into our Top 10.

It was quite a year for Mark Zuckerberg and crew, whose site added a whopping 200 million users. Now, as they brush off the crumbs of MySpace and other competitors, it's time to look for their next meal. They're very, very hungry.

More images: Behind the scenes at the Facebook headquarters

Amazon is writing the book on how to diversify with ingenuity. It generated an estimated $24 billion in revenue last year (up 26% from 2008) not simply through books, which it continues to dominate with the top e-book reader and iPhone reader apps, but also through its growing data storage and computing service, which is fast becoming an online utility for ESPN, eHarmony, and others. Amazon is also expanding its music, video, and electronic check-out services, which are traditionally Apple and Google's strengths. The plot thickens.

It's hard to fathom that Apple opened its App Store less than two years ago, and it already offers more than 140,000 apps, consumers have downloaded around 3 billion apps, and it generates an estimated $1 billion a year. All that should only grow with the much-anticipated release of the iPad. Meanwhile, Apple's acquisition of music-streaming company Lala and its interest in streaming TV shows suggest the seeds of new revenue in a revamped iTunes. Revenue-wise, it was another fruitful year for Apple -- $36.5 billion, a 12% increase from 2008.

Even before the recent launch of its Facebook-like application Buzz, Google was yet again generating plenty of buzz in multiple areas with new products. Once upon a time, it was all about Web search. No more. Google introduced its first device, the Nexus One phone, a new collaborative tool called Wave, and a new music service. Meanwhile, in response to Hulu and other sites, YouTube struck deals with studios and networks to add premium content to the world's top online destination for video. At Google, the search for new opportunities and markets is never-ending.

Shenzhen-based Huawei Technologies shot past Alcatel-Lucent and Nokia Siemens in 2009 to become the world's No. 2 telecom-equipment provider, powered by quality and product upgrades on top of its long-standing low prices.

For most of the past decade, the first renewables company to be listed on the S&P 500 had one overriding goal: driving down the cost of solar-power modules until they could compete with traditional power.

Utilities aren't known for pangs of conscience. But last September, PG&E chief Peter Darbee boldly and publicly resigned from the U.S. Chamber of Commerce over the business council's opposition to global-warming legislation.

Since focusing its R&D on rare diseases and biotech, including vaccines for the likes of H1N1, the Swiss pharma giant has been in a fever of invention. The FDA has approved nine of its drug candidates in 2009 alone.

The world's largest retailer took its boldest leap yet in a quest to green its entire operation with a new plan to rate the sustainability of every product it sells. Tapping its 2 million employees, 100,000 global suppliers, and a consortium of NGO's, scientists, and other businesses, Walmart has grown into the world's greenest retailer.

HP continues its astonishing transformation under CEO Mark Hurd, from an underperforming printer-reliant giant into the world's largest tech company (almost $130 billion a year in revenue), thriving in multiple markets.