Content sharing made super-simple: That’s the pitch for some pretty impressive technology previewed in the latest beta of the upcoming version of Opera Software‘s browser (Opera 10). Called Opera Unite, it basically puts a web server inside your browser, allowing you to easily share pretty much anything on your PC via a custom URL (and a password, if you wish).

All you have to do to enable Opera Unite is to sign up for an account by creating your own user ID and assigning a name for your PC (you can set up several for your account). The URL for a user named denny with a PC named home, for example, would be http://home.denny.operaunite.com/.

Opera Unite is not just a service; it’s a platform that Opera hopes will attract developers. But to get you started, Opera provides a basic set of widgets, including ones for photo-sharing (without having to upload files to Flickr or other services); a chat room; a sticky-note board called The Fridge (because that’s what the interface looks like); general file-sharing; and–for the really ambitious–web site hosting.

I downloaded and installed the technical preview and set up an Opera Unite account in just a couple of minutes, then started playing with widgets. You don’t need to be running Opera to access Opera Unite content — just to serve it up. I got a friend who, using Google’s Chrome browser, was able to post a sticky note to my fridge:

The basic Opera Unite interface, showing the Fridge widget.

There was a bit of lag (we compared notes on instant messaging while waiting for the sticky notes to appear). And I had a bit of trouble getting my usually reliable screen-grab app (Snag-It) to work, making me wonder about what resources Opera Unite requires. But it did work. Here’s what you get as a visitor to a password protected Opera Unite link:

The Opera Unite interface for password-protected content.

One potential fly in the ointment: Opera in its presentation sort of glossed over the potential for copyright problems (like the ones that killed off the original Napster and its ilk). Basically, it sounds like they’re trusting to the honor system (don’t share stuff you have no right to share).

You also have to trust that Opera has plugged all potential security holes — a big question that I’m not equipped to answer. And of course, to make content available, you have to keep your PC on with Opera Unite running, so it’s not exactly a practical alternative to professional web hosting. Still, I think it’s got great potential for empowering non-technical users to dip their toe into content-sharing via the web.

You can learn about Opera Unite and download the preview at unite.opera.com.