So what can you do with Unite? Several things, including:

• Share files, including photo downloading and music streaming.
• Host chats with your friends.
• Run a web server for a simple web site.
• Leave or receive notes on your computer.

Unite requires an Opera account, and an alpha build of Opera 10b (Windows, Mac, Linux).

Opera Unite is a local web server, but it interacts with a proxy server. This means that end users don’t need to establish a firewall or set up port forwarding on their machines. They can just install Opera and go.

After starting a service, you can set three levels of access control: Public (open to anyone), Limited (open to anyone with a password), and Private (available to you). With file sharing and web serving, you also control which directory you want to make available.

Once you have made a directory available, you can send the url — in the form of http://computernickname.yourmyoperausername.operaunite.com/ — to your friends. It’s viewable in any browser, including mobile devices.

Don’t be a dummy: be a safe(r) Unite user

As with any service that lets users share their hard drive’s contents, Opera Unite can be a potential resource hog and security hole. Opera got it right by making these services easy to start or stop, and by supporting restricted access via password. Still, it’s up to users to understand how it all works.

For example, I stumbled across one user’s web server directory that hosted PHP files. Unite, however, is a simple and light-weight HTTP server. There is no PHP, which means that everything — including his database configuration details — is being served as plain text.

So there are two lessons learned:

1. Unite is a basic non-Apache server with no modules that means there’s no PHP, Perl, Python, or even server-side includes available.
2. Don’t share directories with sensitive data, and limit the number of directories that are exposed via Unite

Something else to know: Unite ties you in to the My Opera social network and makes other members aware that your services are running.

Is Unite a game-changer?

I think it depends on what the game is.

I don’t think Unite is compelling enough for most users to switch to Opera as their primary browser or to join the My Opera community. But I would not be surprised if it gained some traction with the geek set.

The concept of Opera Unite is pretty powerful. I can see this being useful as an impromptu office file sharing network, or to stream music from a computer at home to another at a friend’s house party.

Keep in mind that Unite also comes with a JavaScript API that supports file I/O (input/output). In a way, Opera is moving us closer to ubiquitous computing and the browser as OS.

And perhaps that’s the real story of Opera Unite: it is now dead-simple to give as much as you get from the web and use the skills you already have to build new tools.