Google has enabled Cloud Print in Chrome's Dev Channel builds for Windows, but the only option available was to print a test page. Now you can use Google Cloud Print from Gmail's mobile web app for Android and iPhone. The integration lets you print attachments without having to use a full-fledged computer. Since there's no printer with native support for Google Cloud Print, you still need a computer running Google Chrome.
Cloud Print is enabled by default in Chrome Dev Channel and it can be manually enabled in the other builds by typing about:flags in the address bar, clicking "Enable" next to "Cloud Print Proxy" and restarting the browser. To be able to use it, you first need to go to Options >> Under the hood >> Google Cloud Print and log in with a Google account.
Update: According to Google, this feature is also available in Google Docs. "This feature will be rolling out for English speaking users in the US and will work on most phones that support HTML5, such as devices running Android 2.1+ and iOS 3+."