In Oslo, the Tuesday workday is well underway, and that means that Opera Software has unveiled the revolutionary technology breakthrough it started touting last week. The would-be breakthrough turns out to be called Opera Unite, and a downloadable version of Opera 10 that incorporates it is available now. As blogger Kas Thomas somehow managed to guess, it’s a version of the Opera browser with a built-in Web server. And while it’s impossible to judge at this early date whether it’ll “forever change the fundamental fabric of the Web” as Opera promised, it’s a very big idea. Web browsers have always been about bringing information from the Web onto a PC. With Unite, Opera 10 still does that–but it can also fling information from the PC up to the Internet. Unite is a platform that Opera hopes lots of developers will build applications for, but it launches with some apps that Opera developed itself, including a file-sharing service, a chat room, a music player, a photo-sharing tool, and a note-taker. Once you’ve enabled Unite on a Windows, Mac, or Linux computer running Opera 10, the apps are available from any browser on any Internet-connected computer. (You can choose to password protect them, or to leave them open.) Here’s a copy of Firefox accessing the Opera Unite music player–and thereby letting me listen to my music back home from any computer. (Opera also talks about accessing Unite apps from mobile phones, but my iPhone could see my music collection but didn’t let me listen to it.) I’ve tried the music player, photo viewer, and chat room so far. They’re all relatively basic, and the music player also seems to be a tad glitchy–it’s serving up of the music on my hard drive that I pointed it to, but not all of it. Like all of Unite’s initial services, the apps I’ve tried do things that can be accomplished by other means. But the fact that Unite lets you do them with your browser and no additional software, with setup that takes only a few clicks, is fascinating. And as a potentially major new feature that’s truly unique, it’s reason to check out Opera–although the company’s ambitious talk of Unite transforming the Web will only pan out if every browser adds Unite-like features. I’m participating in an Opera Webcast about Unite later today; more thoughts after I’ve had a chance to hear the company explain the concept and answer questions about it.