SAN FRANCISCO, California — Google unveiled a beta version of its Chrome OS Tuesday morning.

The company showed off the operating system, which has been in development for over a year, during a press event here. Also making an appearance at Tuesday’s event was the Chrome Web Store, which we expected to see launch today. If you’re using the Chrome browser, you can visit the store and start installing apps now.

Chrome OS, which doesn’t go into general release until next year, relies entirely on web-based applications for basic productivity tasks like mail, document editing, photo sharing, social networking and reading news. Its inner workings are based on Google’s own Chrome browser.

To get around the connectivity problem inherent to web-based apps, Google says every Chrome OS laptop will ship with both wi-fi and cellular connections. The company has partnered with Verizon — when you buy a Chrome OS laptop, you get 100MB of free data per month for two years. There are no long-term contracts. If you want to upgrade, you only pay for what you need. Chrome OS users can buy a day pass from Verizon, or choose from a few long-term plans starting at $10 per month.

Acer and Samsung Chrome OS laptops will go on sale in mid-2011, with more OEMs to follow, the company says.

In the meantime, Google is launching a pilot program to get hardware running Chrome OS into developers’ hands. Early adopters can sign up to get a black, unbranded Chrome OS notebook, codenamed “Cr-48.”

Google VP of product management Sundar Pichai held one up during the event — it’s a full-sized laptop with a 12.1″ screen, an Intel Atom processor, a world-mode 3G radio, a flash memory drive, and it has a built-in “jailbreaking” mode so you can hack it. Google is also giving away a few of the pilot laptops to its Facebook fans.

From what we’ve seen so far, Chrome OS is extremely fast (the demo we saw was running on the Cr-48 laptop) and, provided you already have a Google account, it literally takes under a minute to get up and running.

Pichai, who has been using ChromeOS for six months, continuously gushed about its speed, which was evident during the demos.

“By building an experience based totally on the web, we’ve made all of the user experiences instant,” he said.

When you launch Chrome OS for the first time, you log in with your Google account and immediately see a grid view of pre-installed web apps like Gmail, Google Reader, a text editor and apps from The New York Times and other partners. All of the apps shortcuts live inside a browser window, so if you want to start surfing, you just type into the URL bar. Chrome OS also has built-in controls for syncing, so any user can log into any Chrome OS laptop and get the desktop and the same experience they’re used to.

From the home screen, you go to the Web Store and install single-serving apps that are enhanced versions of those already available on the web. The download-and-install option gives you a few more niceties, like the ability to answer e-mail, work on your docs and play games when you don’t have a web connection.

The Web Store launched Tuesday in the U.S. with around 500 applications. Other countries and regions will follow soon, Google says.

These installable web apps square well with the cloud-based direction we’re currently heading. Whether you’re reading a book, writing e-mails, or sharing documents, cloud-based apps allow you to stay synced across your phone and all of your computers.

Google CEO Eric Schmidt showed up at Tuesday’s event to drive home his belief the time is right to release Chrome OS.

“We finally have a viable third choice for an operating system on the desktop,” he said.

“We’re now able to build web applications that are at the scale and power of desktop applications,” he said, citing the speed an security innovations made by Firefox, as well as new technologies like HTML5, as the advancements that paved the way to a web-based operating system.

In a round of demos, Amazon showed off two apps — a web app version of its Kindle reader, and a product browser called Windowshop. We saw apps from Sports Illustrated and The New York Times. They both looked like a rich news readers, with enhanced navigation heavy on HTML5 and JavaScript, all the recent headlines, photos and videos loaded dynamically. Curiously, there were no ads on display in the apps.

Many of the apps are free or available under a freemium model. Some of them, like games, cost $2 or $3 each. You buy apps from the Chrome Web Store using Google Checkout, so you need to have a Google account to buy apps.

Google has also partnered with Citrix for easy installation of enterprise apps with secure, company-only sharing features. The Citrix platform will launch during the first half of 2011, the company says.

We’ve seen hints of the Chrome OS and Web Store launch in recent weeks. In Novemeber, rumors that OEMs were prepping laptops loaded with Chrome OS surfaced. Just last week, Google debuted Chrome 8, the first version of its web browser with the built-in ability to plug into the Chrome Web Store. TechCrunch uncovered an e-mail from Google telling developers to get ready for the Web Store launch. In the wee hours of Tuesday morning, the company unceremoniously posted a page for getting started with its Google Cloud Print service that lets you print a page from a laptop or mobile to any printer hooked up to a Windows PC with internet access.

Google admits there is still much work to be done on Chrome OS, and the bug tracking page shows numerous stability problems and hardware shortcomings.

“We’ve made amazing progress but we still have a lot of work to do,” Pichia said.

If you want to try it out today, you can join Google’s developer program and install Chrome OS on a wide range of hardware. But as Google VP of engineering Linus Upson said Tuesday, the process is still rather hairy for non-geeks.

“The question is, how comfortable are you compiling from source,” he joked.

See also:

• Rumor: First Chrome OS Notebooks Land This Month
• Google Chrome OS: Ditch Your Hard Drives, the Future Is the Web
• Chrome Store Possibly Launching Dec. 7
• Chrome Web Store Is Now Open for Developers
• Chrome 8 Arrives
• Mozilla Shows Off Plans for an Open Web App Store

That’s the question Google is hoping to answer with Chrome OS, the open source operating system centered entirely around its Chrome browser. All your apps — e-mail, communications, docs, photo management — are delivered through the web browser, which sits on a lightweight Linux-powered desktop.

The company debuted Chrome OS Thursday morning during a press event at its headquarters in Mountain View, California. Wired.com’s Dylan Tweney was there to bring us all the details, and you can expect a post from him Thursday morning [Update: Dylan's post is up on Gadget Lab].

In the meantime, Google has posted a video (below) making an argument for why you’d want an operating system that funnels all of your productivity tasks through a browser: “It just gives you the internet, which is all most of us use our computers for now, anyways.”

And here’s a demonstration of the user interface. It’s striking — the browser is all there is to it.

Read the overview on the Google Blog. Also, be sure to check out some of the initial design specs, including the OS’s ability to auto-update silently and daily.

See Also:

• Five Questions About Google Chrome OS
• Google Takes On IE, Firefox With Chrome Web Browser
• Google Shows Off Chrome Themes With Cool YouTube Hack