It was a watershed year for many technology platforms, with social networks and mobile devices rising up to rival personal computers as options for developers building applications and services. But which system deserves the title of Technology Platform of the Year? That's today's category in The Flashies, our year-end technology awards. Your votes will determine the winner. And the nominees are ...

As with previous categories, free to offer a write-in candidate in the comments below. Other readers will be able to support your nomination by logging in and clicking the "like" button next your comment. We'll announce all the Flashies winners in a post at the end of the year.

Continue reading for detailed descriptions of the nominees for today's category, and our reasons for including them. And be sure to check back next week as we continue to roll out more Flashies categories.

Facebook: Millions of people use Facebook to connect with their friends, but the social network doubles as an application platform, citing usage by more than 1 million developers and entrepreneurs around the world. RealNetworks CEO Rob Glaser identified Facebook and the iPhone as "the new platforms" earlier this year, comparing them to the IBM PC, Windows and the Internet for their potential to support new types of applications and companies.

Firefox 3.5: The latest upgrade to Mozilla Firefox, released in June, added advanced video support and many other enhanced features, such as the ability to determine your location (with your permission) when using the browser on mobile computers. The release helped Firefox build momentum, approaching 25 percent market share despite Microsoft's continued inclusion of Internet Explorer in its dominant Windows operating system.

iPhone 3GS: The "S" stands for "speed," Apple promised, and this zippy new release of the company's mobile operating system helped to fuel the iPhone's rise as the smart-phone platform to beat. But where the iPhone really stands out is as a platform, with Apple now boasting more than 100,000 apps available for the device. That puts the iPhone well ahead of Google's Android in raw numbers of applications, but one big question going into 2010 is whether Apple can continue to fend off its growing lineup of rivals.

Kindle DX: A platform? You bet. Books are apps, after all. And despite the fact that the market for digital reading remains pretty small, Amazon.com is leading the charge toward electronic books with its Kindle readers. Then again, without specific sales numbers, we're left to take the company's word that the demand is strong. Kindle DX, unveiled in May, refreshed Amazon's lineup in the face of growing competition from Sony and many others. Amazon also went multi-device with Kindle apps for iPhone. and Windows PCs, with Kindle for Macs and BlackBerry coming soon.

Mac OS X 10.6: Snow Leopard, the latest upgrade to Apple's operating system focused more on underlying performance than on snazzy new features for end users, available for a mere $29 to existing users of Mac OS X Leopard machines. The upgrade has helped to keep Macs humming, bolstering Apple's efforts to chip away at the dominant market share of Microsoft's Windows operating system.

Twitter: Some people might contend that Twitter doesn't really qualify as a platform. But given the booming number of services and applications leveraging the Twitter API and tapping into Twitter feeds, there's no question that the microblogging site has generated a thriving ecosystem. The key questions going into the next year are whether Twitter can make money, whether it will be acquired, and whether it can shore up its infrastructure and avoid high-profile incidents such as last night's embarrassing hack.

Ubuntu 9.1: Dubbed "Karmic Koala," this update to the popular Ubuntu Linux distribution added features including a new "Ubuntu Software Center," designed to make it easier for users to install, update and manage software applications in the operating system. Future releases of Ubuntu are expected to further enhance the Software Center, aiming to make the operating system even friendlier to applications and the people using them.

Windows 7: Microsoft might just have salvaged the reputation of its flagship product with the debut of this new Windows version. Windows 7, released to the public in October, was designed to be more lightweight and stable than its predecessor, while making it easier to manage open windows and set up home networks. The release hasn't been without complication, but better performance and application compatibility have put Windows 7 well above the 3-year-old Windows Vista in the minds of many PC users.

Click here to see previous Flashies categories. More next week.