Apple's new Mac Mini now ships with server software, but Apple's suggested uses are vanilla. With 1TB of storage and plenty of power, let's put it to good use and stream some music and movies over the Intertubes.
Snow Leopard Server  can do a lot of useful stuff right out of the box: You can file share, sync contacts, host a Web site. Snore. Personal servers are cool because they let you access your stuff from anywhere. But too many of Apple's sharing apps (like Home Sharing on iTunes) require that you be on the same local network. What if you want to roam the earth with constant access to Madonna's Immaculate Collection?
You'll need a few tools, all of them free (except the Mac Mini, which will set you back $1,000. But for our purposes, any Mac will work.)
Step one: get Opera 10 with Unite. Opera's new browser is incredible: it lets you create an impromptu music server  with utter simplicity. (You can also set it up to stream movies that are stored on your local machine, or share bunch of other junk like photos and documents; but I digress). Check it out the rest of the features and download here ; for simplicity's sake, we'll just stick with the music portion of this endeavor. Or watch the YouTube video:
Once you have your Opera music server up and running, you'll realize you can share your entire collection, streamable, by sending your friends a simple Web URL. The problem: the URL is long, nasty and forgettable. Buy a domain name (http://your-music-site.com ) for $10 from a registrar like GoDaddy , and set it up to forward to that ugly Opera domain. Now you can tell people to head to your-music-site.com, instead of belching out a long Web address. (Don't worry; your Opera server is password-protected by default, so just knowing your domain name isn't enough for some freeloader to start listening to your tunes.)
Once you've got Web access to your Opera music server all setup, you'll realize a curious problem: your Opera music server is only running when Opera is running. You could keep Opera alive on your Mac Mini at all hours, but that seems excessive for something that you might only use occasionally. If you want to really geek out, get TweetMyMac .
TweetMyMac lets you control your home computer (in this case, your Mac Mini server) from anywhere using commands over Twitter. You create a Twitter account for your Mac, and then send it direct messages from your own authorized Twitter account telling it what to do. The list of commands is unbelievable: not only can you shut down, logout or sleep your Mac from anywhere, you can also open and quit apps, get screenshots, lock it, mute it, and get its IP address. Next time you want to show your friend a song, pull out your phone, tweet your Mac Mini Server to open Opera, and then go to your new custom domain. All your music will be laid out before you, ready to stream.
Better yet, you can stream the same way on the iPhone by going to your new music URL with Mobile Safari. (Some stream-to-your-iPhone apps  exist, but none of them do exactly this, or work very well.)
Just set up the other Opera Unite widgets, and you can do the same thing with all your movies and photos. If you want to see how your Mini server is running at any given time, try iStat Server  for iPhone.